C. BECK

Abstract: alpha-d coincidence data were studied for the 6Li + 59Co reaction at E(lab) = 29.6 MeV. By using a kinematic analysis, it was possible to identify which process, leading to the same final state, has the major contribution for each of the selected angular regions. Contributions of the 6Li sequential and direct breakup to the incomplete fusion/transfer process were discussed by considering the lifetimes obtained by using a semiclassical approach, for both breakup components.

Abstract: An experimental overview of reactions induced by the stable, but weakly-bound nuclei 6Li, 7Li and 9Be, and by the exotic, halo nuclei 6He, 8B, 11Be and 17F on medium-mass targets, such as 58Ni, 59Co or 64Zn, is presented. Existing data on elastic scattering, total reaction cross sections, fusion processes, breakup and transfer channels are discussed in the framework of a CDCC approach taking into account the breakup degree of freedom.

Abstract: Resonances in the 12C(16O,gamma)28Si radiative capture process at energies around the Coulomb barrier have been probed using the very selective 0° Dragon spectrometer at Triumf and its associated BGO gamma-array. For the first time the full level scheme involved in this process has been measured and shows previously unobserved gamma-decay to doorway states around 11 MeV in 28Si.

Abstract: Charged-particle and gamma decays in 24Mg* are investigated for excitation energies where quasimolecular resonances appear in 12C+12C collisions. Various theoretical predictions for the occurrence of superdeformed and hyperdeformed bands associated with resonance structures with low spin are discussed within the measured 24Mg* excitation energy region. The inverse kinematics reaction 24Mg+12C is studied at Elab(24Mg)=130 MeV, an energy that enables the population of 24Mg states decaying into 12C+12C resonant breakup states. Exclusive data were collected with the Binary Reaction Spectrometer in coincidence with Euroball IV installed at the Vivitron tandem facility at Strasbourg. Specific structures with large deformation were selectively populated in binary reactions, and their associated gamma decays studied. Coincident events associated with inelastic and alpha-transfer channels have been selected by choosing the excitation energy or the entry point via the two-body Q values. The analysis of the binary reaction channels is presented with a particular emphasis on 24Mg-gamma, 20Ne-gamma, and 16O-gamma coincidences. New information (spin and branching ratios) is deduced on high-energy states in 24Mg and 16O, respectively.

Abstract: nvestigations on the influence of the neutron enrichment on the decay channels of excited nuclei are presented. Characteristics of fragments with charge 6 \le Z \le 28 emitted in 78,82{Kr}+40Ca at 5.5 MeV/A reactions were measured at the GANIL facility. Data are compatible with an emission process from compound nucleus and are discussed in the framework of the transition state model.

Abstract: The reactions induced by the weakly bound 6Li projectile interacting with the intermediate mass target 59Co were investigated. Light charged particles singles and α�d coincidence measurements were performed at the near barrier energies Elab=17.4, 21.5, 25.5 and 29.6 MeV. The main contributions of the different competing mechanisms are discussed. A statistical model analysis, Continuum-Discretized Coupled-Channels (CDCC) calculations and two-body kinematics were used as tools to provide information to disentangle the main components of these mechanisms. A significant contribution of the direct breakup was observed through the difference between the experimental sequential breakup cross section and the CDCC prediction for the non-capture breakup cross section.

Abstract: In a recent experiment performed at Triumf using the Dragon 0° spectrometer and its associated BGO array we have measured for the first time the full gamma decay of the radiative capture channel close to the Coulomb barrier. This measurement has been performed at 3 energies Ecm = 8.5, 8.8 and 9 MeV. We have extracted a radiative capture cross section more than five times larger than what had been previously observed. A selective contribution of the entrance spins 5� and 6+ has also been evidenced whereas 1� to 3� spins are predicted to be predominant by coupled-channel calculations. At Ecm = 9 MeV, stronger structural behaviour appears which is characterised by a larger total cross section and also by the particularly strong feeding of the 28Si prolate 4+ state at 9.16 MeV. This level is explained by several models in terms of 12C-16O cluster sub-structure. Our data is compared to such cluster-model predictions and the agreement is quite good.

Abstract: Investigations into the role of the N/Z ratio on the decay modes of compound nuclei are presented. Characteristics of fragments with atomic number 6<=Z<=28 and light charged particles emitted in 78,82Kr+40Ca at 5.5 MeV/A reactions were measured at the GANIL facility using the 4pi-INDRA array. Data are compatible with an emission process from a compound nucleus. Persistence of structure effects and emission before full separation of fission fragments are evidenced from elemental cross-sections and coincidence data between light charged particles and fragments. Data are discussed in the framework of the transition state model.

Abstract: The 12C(16O,gamma)28Si radiative capture reaction has been studied at energies close to the Coulomb barrier at Triumf (Vancouver) using the Dragon spectrometer and its associated BGO array. It has been observed that the gamma decay flux proceeds mainly via states around 10â��11 MeV and via the direct feeding of the 28Si 3₁^- (6879 keV) and 4₂⁺ (6888 keV) deformed states. A discussion is presented about this selective feeding as well as perspectives for the use of novel detection systems for the study of light heavy-ion radiative capture reactions.

Abstract: The occurence of �exotic� shapes in light N = Z alpha-like nuclei is investigated for 24Mg+12C and 32S+24Mg. Various approaches of superdeformed and hyperdeformed bands associated with quasimolecular resonant structures with low spin are presented. For both reactions, exclusive data were collected with the Binary Reaction Spectrometer in coincidence with EUROBALL IV installed at the VIVITRON Tandem facility of Strasbourg. Specific structures with large deformation were selectively populated in binary reactions and their associated gamma-decays studied. The analysis of the binary and ternary reaction channels is discussed.

Abstract: The reaction 32S (165.4 MeV) + 24Mg is studied using the binary reaction spectrometer (BRS) coupled to the Euroball Ge-detector array. Particle�particle�γ and particle�γ�γ coincidences have been examined together with γ�γ-only coincidences for the fusion-evaporation residues. Recent reports of evidence for hyper-deformation from angular correlations in similar data are investigated. Analogous out-of-plane angular correlations are observed but attributed to reactions with the target contaminants 16O and 12C. This is consistent with the contamination observed in the γ�γ-only data.

Abstract: The structure of 56Ni is studied by using the non-relativistic Skyrme Hartree�Fock and the relativistic Hartree approximation in an axially deformed cylindrical coordinate. We found several intrinsic excited states, including the spherical ground-state solution. Without including any extra α-cluster correlations, the possible cluster configurations of the resonance states are analyzed, showing the multiple N = Z, α-nucleus-like cluster structures for hyper-deformed states, but, contrary to the recent experimental possibility of a ternary fission decay, we predict a two-cluster or symmetric fission configuration for the hyper-hyperdeformed state.

Abstract: The radiative capture process of the 12C+12C and 12C+16O reactions has been studied using the very selective 0° Dragon spectrometer at Triumf and its associated BGO γ-array. The experiments have been performed at energies around the Coulomb barrier where resonances in the process have been reported. Our results show previously unobserved γ-decay to doorway states in the 24Mg and 28Si respectively around 10 to 12 MeV. The nature of the states is discussed and two scenarii are proposed.

Abstract: Cross sections, kinetic energy and angular distributions of fragments with charge 6 � Z � 28 emitted in 78,82Kr+40C at 5.5 MeV/A reactions were measured at the GANIL facility using the INDRA apparatus. This experiment aims to investigate the influence of the neutron enrichment on the decay mechanism of excited nuclei. Data are discussed in comparison with predictions of transition state and Hauser-Feshbach models.

Abstract: Charged particle and gamma decays in light alpha-like nuclei are investigated for 24Mg+12C. Various theoretical predictions for the occurence of superdeformed and hyperdeformed bands associated with resonance structures with low spin are presented. The inverse kinematics reaction 24Mg+12C is studied at Elab(24Mg) = 130 MeV. Exclusive data were collected with the Binary Reaction Spectrometer in coincidence with EUROBALL IV installed at the VIVITRON Tandem facility at Strasbourg. Specific structures with large deformation were selectively populated in binary reactions and their associated gamma decays studied. Coincident events from $\alpha$-transfer channels were selected by choosing the excitation energy or the entry point via the two-body Q-values. The analysis of the binary reaction channels is presented with a particular emphasis on 20Ne-gamma and 16O-gamma coincidences.

Abstract: Using a unique two-arm detector system for heavy ions (BRS, binary reaction spectrometer) coincident fission events have been measured from the decay of 60Zn and 56Ni compound nuclei formed at 83�88 MeV excitation energy. From the binary coincidences inclusive and exclusive cross sections for fission channels with differing losses of charge were obtained. Narrow out-of-plane correlations corresponding to coplanar decay are observed for two fragments emitted in binary events, and in the data for ternary decay with missing charges from 4 up to 8. Differential cross sections for the different binary and ternary fission channels are obtained. The ternary cluster fission can be explained by the statistical decay from equilibrated compound nuclei with hyper-deformed shapes with angular momenta around 45�52 h.

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Abstract: The 24Mg + 24Mg reaction has been studied at the Legnaro Tandem at a CM bombarding energy of 45.7 MeV where a narrow and high spin resonance has been reported previously. The decay of the resonance into the inelastic and fusion�evaporation channels has been investigated. The ON and OFF resonance decay yields have been measured using, for the inelastic channels, the fragment spectrometer PRISMA and the γ array CLARA, and, for the fusion�evaporation channels, the Si array EUCLIDES and the γ array GASP. Strong resonant effects have been observed in the inelastic channels involving the Click to view the MathML source and Click to view the MathML source states of the 24Mg ground state band. Weaker effects are also seen in certain fusion�evaporation channels. The properties of the studied resonance are in agreement with molecular model predictions. It is also proposed that the narrow and high spin 24Mg + 24Mg resonance corresponds to the formation of a fast rotating and highly prolate deformed 48Cr after a Jacobi shape transition and just before fission.

Abstract: The $^{24]$Mg + $^{24}$Mg reaction has been studied at the Legnaro Tandem at a CM bombarding energy of 45.7 MeV where a narrow and high spin resonance has been reported previously. The decay of the resonance into the inelastic and fusion-evaporation channels has been investigated. The ON and OFF resonance decay yields have been measured using, for the inelastic channels, the fragment spectrometer PRISMA and the $\gamma$ array CLARA, and, for the fusion-evaporation channels, the Si array EUCLIDES and the $\gamma$ array GASP. The resonant effects observed in both experiments are discussed and it is suggested that the resonance populates a deformed $^{48}$Cr after a Jacobi shape transition.

Abstract: Coincidences between two heavy fragments have been measured from the fission of 56Ni compound nuclei formed in the 32S + 24Mg reaction at E lab( ^32S ) = 165.4 MeV. A unique experimental set-up consisting of two large-area position-sensitive (x, y) gas detector telescopes has been used allowing the complete determination of the observed fragments and their momentum vectors. In addition to binary fission events with subsequent particle evaporation, narrow out-of-plane correlations are observed for two fragments emitted in purely binary events and in events with a missing charge consisting of 2α - and 3α -particles (12C). These events are interpreted as ternary cluster decay from 56Ni nuclei at high angular momenta through hyper-deformed shapes.

Abstract: he heavyion radiative capture reaction 12C(16O,$\gamma$)28Si has been studied at three energies on( ELab = 20.0 and 21.2 MeV) and off( ELab = 20.7 MeV) resonance at Triumf (Vancouver) using the stateoftheart Dragon 0° spectrometer and its very efficient associated BGO $\gamma$ array. Intermediate states around Ex = 11.5 MeV, carrying a large part of the resonant flux have been observed for the first time in this system. The nature of those doorway states is discussed in terms of recently calculated cluster bands in 28Si. The results are compared to a recent similar investigation of the 12C(12C,$\gamma$)24Mg reaction.

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Abstract: The influence on the fusion process of coupling to collective degrees of freedom has been explored. The significant enhancement of the fusion cross section at sub-barrier energies was compared to predictions of one-dimensional barrier penetration models. This was understood in terms of the dynamical processes arising from strong couplings to collective inelastic excitations of the target and projectile. However, in the case of reactions where at least one of the colliding nuclei has a sufficiently low binding energy, for breakup to become an important process, conflicting model predictions and experimental results have been reported in the literature. Excitation functions for sub- and near-barrier total (complete + incomplete) fusion cross sections have been measured for the 6,7Li+59Co reactions. Elastic scattering as well as breakup/transfer yields have also been measured at several incident energies. Results of Continuum-Discretized Coupled-Channel (Cdcc) calculations describe reasonably well the experimental data for both reactions at and above the barrier. A systematic study of 4,6He induced fusion reactions with a three-body Cdcc method is presented. The relative importance of breakup and bound-state structure effects on total fusion (excitation functions) is particularly investigated. The four-body Cdcc model is being currently developed.

Abstract: The heavy-ion radiative capture reaction, 12C(12C,gamma), has been investigated at energies both on- and off-resonance, with a particular focus on known resonances at Ec.m.=6.0, 6.8, 7.5, and 8.0 MeV. Gamma rays detected in a BGO scintillator array were recorded in coincidence with 24Mg residues at the focal plane of the DRAGON recoil separator at TRIUMF. In this manner, the relative strength of all decay pathways through excited states up to the particle threshold could be examined for the first time. Isovector M1 transitions are found to be a important component of the radiative capture from the Ec.m.=6.0 and 6.8 MeV resonances. Comparison with Monte Carlo simulations suggests that these resonances may have either J=0 or 2, with a preference for J=2. The higher energy resonances at Ec.m.=7.5 and 8.0 MeV have a rather different decay pattern. The former is a clear candidate for a J=4 resonance, whereas the latter has a dominant J=4 character superposed on a J=2 resonant component underneath. The relationship between these resonances and the well-known quasimolecular resonances as well as resonances in breakup and electrofission of 24Mg into two 12C nuclei are discussed. ©2007

Abstract: Exotic-deformation effects in 46Ti nucleus were investigated by analysing the high-energy gamma-ray and the alpha-particle energy spectra. One of the experiments was performed using the charged-particle multi-detector array ICARE together with a large volume (4"x4") BGO detector. The study focused on simultaneous measurement of light charged particles and gamma-rays in coincidence with the evaporation residues. The experimental data show a signature of very large deformations of the compound nucleus in the Jacobi transition region at the highest spins. These results are compared to data from previous experiments performed with the HECTOR array coupled to the EUROBALL array, where it was found that the GDR strength function is highly fragmented, strongly indicating a presence of nuclei with very large deformation.

Abstract: The 46Ti* compound nucleus, as populated by the fusion-evaporation reaction 27Al + 19F at the bombarding energy of Elab = 144 MeV, has been investigated by charged particle spectroscopy using the multidetector array ICARE at the VIVITRON tandem facility of the IReS (Strasbourg). The light charged particles and high-energy γ-rays from the GDR decay have been measured in coincidence with selected evaporation residues. The CACARIZO code, a Monte Carlo implementation of the statistical-model code CASCADE, has been used to calculate the spectral shapes of evaporated α-particles which are compared with the experimental coincident spectra. This comparison indicates the signature of large deformations (possibly superdeformed and hyperdeformed shapes) present in the compound nucleus decay. The occurrence of the Jacobi shape transition is also discussed in the framework of a newly developed rotating liquid drop model.

Abstract: The inclusive energy distributions of the complex fragments (3<=Z<=7) emitted from the bombardment of 12C by 20Ne beams with incident energies between 145 and 200 MeV have been measured in the angular range 10°<=thetalab<=50°. Damped fragment yields in all the cases have been found to have the characteristic of emission from fully energy equilibrated composites. The binary fragment yields are compared with the standard statistical model predictions. Whereas Li and Be fragments yields are in agreement with statistical-model calculations, enhanced yields of entrance channel fragments (5<=Z<=7) indicate the survival of orbiting-like process in 20Ne+12C system at these energies.

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Abstract: The influence on fusion of coupling to the breakup process is investigated for reactions where at least one of the colliding nuclei has a sufficiently low binding energy for breakup to become an important process. Elastic scattering, excitation functions for sub- and near-barrier fusion cross sections, and breakup yields are analyzed for 6,7Li+59Co. Continuum-discretized coupled-channels (CDCC) calculations describe well the data at and above the barrier. Elastic scattering with 6Li (as compared to 7Li) indicates the significant role of breakup for weakly bound projectiles. A study of 4,6He induced fusion reactions with a three-body CDCC method for the 6He halo nucleus is presented. The relative importance of breakup and bound-state structure effects on total fusion is discussed.

Abstract: Two-particle correlation functions, involving protons, deuterons, tritons, and α-particles, have been measured at very forward angles (0.7°less-than-or-equals, slantθlabless-than-or-equals, slant7°), in order to study projectile-like fragment (PLF) emission in E/A = 44 and 77 MeV 40Ar + 27Al collisions. The observed correlations are similar for the two reactions at E/A=44 and 77 MeV, except for peaks originating from resonance decays, which are larger at the lower bombarding energy. Particle-velocity gated correlation functions are presented, and possible implications on the time sequence of the light charged particles, emitted from the PLF, are discussed.

Abstract: A new experiment to determine the thermonuclear cross section of the 12C(alpha,gamma)16O reaction has been performed in regular kinematics using an intense alpha-particle beam of up to 340 µA from the Stuttgart DYNAMITRON. For the first time, a 4pi-germanium-detector setup has been used to measure the angular distribution of the gamma rays at all angles simultaneously. It consisted of an array of nine EUROGAM high-purity Ge detectors in close geometry, actively shielded individually with bismuth germanate crystals. The 12C targets were isotopically enriched by magnetic separation during implantation. The depth profiles of the implanted carbon in the 12C targets were determined by Rutherford backscattering for purposes of cross-section normalization and absolute determination of the E1 and E2 S factors. Angular distributions of the gamma decay to the 16O ground state were measured in the energy range Ec.m.=1.30�2.78 MeV and in the angular range (lab.) 30°�130°. From these distributions, astrophysical E1 and E2 S-factor functions vs energy were calculated, both of which are indispensable to the modeling of this reaction and the extrapolation toward lower energies. The separation of the E1 and E2 capture channels was done both by taking the phase value phi12 as a free parameter and by fixing it using the results of elastic alpha-particle scattering on 12C in the same energy range.

Abstract: The dynamical cluster-decay model (DCM) is developed further for the decay of hot and rotating compound nuclei (CN) formed in light heavy-ion reactions. The model is worked out in terms of only one parameter, namely the neck-length parameter, which is related to the total kinetic energy TKE(T) or effective Q value Qeff(T) at temperature T of the hot CN and is defined in terms of the CN binding energy and ground-state binding energies of the emitted fragments. The emission of both the light particles (LP), with A<=4,Z<=2, as well as the complex intermediate mass fragments (IMF), with 4<A<20,Z > 2, is considered as the dynamical collective mass motion of preformed clusters through the barrier. Within the same dynamical model treatment, the LPs are shown to have different characteristics compared to those of the IMFs. The systematic variations of the LP emission cross section sigmaLP and IMF emission cross section sigmaIMF calculated from the present DCM match exactly the statistical fission model predictions. A nonstatistical dynamical description is developed for the first time for emission of light particles from hot and rotating CN. The model is applied to the decay of 56Ni* formed in the 32S+24Mg reaction at two incident energies Ec.m. = 51.6 and 60.5 MeV. Both the IMFs and average TKE^{[underaccent underbar [below]} spectra are found to compare resonably well with the experimental data, favoring asymmetric mass distributions. The LPs' emission cross section is shown to depend strongly on the type of emitted particles and their multiplicities.

Abstract: We study the 16O+58Ni deep inelastic reaction by using coincident charged techniques. Inclusive as well as exclusive data of the C, N, and O fully-damped fragments and their associated light charged particles (p, d, t, and α-particles) have been collected at the IReS Strasbourg VIVITRON Tandem facility. The velocity distributions of the emitted protons and the associated multiplicity polar plots are analyzed by means of a model which describes simultaneously the nonequilibrium and the evaporative (equilibrated) components of a deep inelastic reaction mechanism. Estimates on polarization phenomena as well as the associated "decay times" of the reaction have been obtained. The hypothesis of a new "fan effect" is proposed for the proton sequential emission in the deep inelastic scattering of 16O+58Ni at 8.25 MeV/nucleon.

Abstract: The inclusive energy distributions of fragments with Z >= 3 emitted from the bombardment of 12C by 20Ne beams with incident energies between 145 and 200 MeV have been measured in the angular range thetalab~10°-50°. Damped fragment yields in all cases have been found to be characteristic of emission from fully energy equilibrated composites; for B and C fragments, average Q values, <Q>, were independent of the center-of-mass emission angle (thetac.m.), and the angular distributions followed a ~1/sinthetac.m.-like variation, signifying long lifetimes of the emitting dinuclear systems. Estimates of total yields of these fragments have been found to be much larger than those predicted by the standard statistical model. This may be indicative of the survival of an orbiting-like process in the 12C+20Ne system at these energies.

Abstract: The 46Ti* compound nucleus, as populated by the fusion--evaporation reaction 27Al + 19F at the bombarding energy of 144MeV, has been investigated by charged particle spectroscopy using the multidetector array ICARE at the VIVITRON tandem facility of the IReS (Strasbourg). The light charged particles have been measured in coincidence with evaporation residues. The CACARIZO code, a Monte Carlo implementation of the statistical model code CASCADE, has been used to calculate the spectral shapes of evaporated alpha -particles which are compared with the experimental spectra. This comparison indicates the possible signature of large deformations of the compound nucleus.

Abstract: A beam of 26Mg at 160 MeV incident on a thin target of 150Nd was used to initiate deep-inelastic and multi-nucleon transfer reactions. The gamma-decay of the fragments produced in the reaction was studied using the EUROBALL IV array of escape suppressed Ge detectors at Strasbourg combined with the binary reaction spectrometer used to detect the projectile-like fragments. Preliminary results from the experiment are presented.

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Abstract: The gamma-decay of fragments from deep-inelastic and multi-nucleon transfer processes which occur when a beam of 26Mg at 160MeV is incident on a thin 150Nd target was studied using the EUROBALL IV array of escape suppressed Ge detectors at Strasbourg. The good resolving power of EUROBALL IV was further increased by combining it with the Binary Reaction Spectrometer (BRS), used for the detection of projectile-like fragments. The BRS allows full kinematic reconstruction of the binary reaction allowing crucial Doppler corrections of gamma-ray spectra to be performed. Some preliminary results are presented.

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Abstract: Fusion cross section excitation functions were measured for the 6;7Li+59Co systems (12 < Elab < 26 MeV)aiming the investigation of the effect of the breakup process on the fusion cross section. The experimental method consisted on the detection of g-rays from the evaporation residues. Coupled channels calculations have been performed for both systems. The comparison to the experimental results support the conclusion that there is neither supression nor enhancement at energies above the coulomb barrier. A slight enhancement at energies below the barrier is observed for the 6Li+59Co cross section over the one for 7Li+59Co. In order to better quantify the effect of the breakup process, coincidence measurements for the breakup products are being performed.

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Abstract: In-plane and out-of-plane correlations of light charged particles and neutrons emitted in the 35Cl (260 MeV)+24Mg complete fusion reaction have been measured to investigate deformation and angular momentum effects upon the decay of 59Cu compound nucleus. An array of 21 BaF2 crystals has been used to identify the light charged particles (Z<=4) and neutrons emitted in coincidence with heavy fragments (Z>=5) detected in six ionization chamber telescopes. Coincident energy spectra and angular distributions of neutrons, protons, and alpha-particles have been described by the statistical-model calculations with nuclear level densities tuned to take account of deformation effects in the emitters. This spin-dependent approach suggests the onset of large nuclear deformation in 59Cu at high spin. This conclusion is consistent with the recent observation of a superdeformed band in the 59Cu nucleus.

Abstract: The collective clusterization process, proposed for intermediate mass fragments (IMFs, 4$<$A$le$28, 2$<$Z$le$14) emitted from the hot and rotating compound nuclei formed in low energy reactions, is extended further to include also the emission of light particles (LPs, A$le$4, Z$le$2) from the fusion-evaporation residues. Both the LPs and IMFs are treated as the dynamical collective mass motion of preformed clusters through the barrier. Compared to IMFs, LPs are shown to have different characteristics, and the predictions of our, so-called, dynamical cluster-decay model are similar to those of the statistical fission model.

Abstract: Following the commissioning of the PRISMA large-acceptance spectrometer, installed at the Laboratori Nazionali di Legnaro (LNL), an international nuclear-structure collaboration has started to develop a large $gamma$-ray setup to be installed in the target position of the spectrometer. The array is based on the EUROBALL composite CLOVER detectors. In this contribution the CLOVER detector array is described and its expected performance figures discussed. This new setup, by using the high-intensity heavy-ion beams provided by the LNL ALPI linac, will push the study of nuclear structure towards moderately neutron-rich nuclei by means of quasi-elastic and deep inelastic reactions.

Abstract: The γ-decay properties of 24Mg excited states are investigated in the inverse reaction24Mg+12C at Elab(24Mg) = 130 MeV. At this energy the direct inelastic scattering populates a24Mg* energy region where12C+12C breakup resonances can occur. Very exclusive data were collected with the Binary Reaction Spectrometer (BRS) in coincidence with EUROBALL installed at the VIVITRON Tandem facility of the IReS at Strasbourg. The experimental detection system is described and preliminary results of binary reaction coincidence data are presented.

Abstract: Nuclear alpha-clustering has been the subject of intense study since the advent of heavy-ion accelerators. Looking back for more than 40 years we are able today to see the connection between quasimolecular resonances in heavy-ion collisions and extremely deformed states in light nuclei. For example superdeformed bands have been recently discovered in light N=Z nuclei such as 36Ar, 40Ca, 48Cr, and 56Ni by γ-ray spectroscopy. The search for strongly deformed shapes in N=Z nuclei is also the domain of charged-particle spectroscopy, and a number of these nuclei have been studied with the charged particle multidetector array ICARE at the VIVITRON. Recently the search for γ-decays in 24Mg has been undertaken in a range of excitation energies where previously nuclear molecular resonances were found in 12C+12C collisions. The breakup reaction 24Mg+12C has been investigated at an energy which corresponds to a 12C+12C resonance. Very exclusive data were collected with the Binary Reaction Spectrometer in coincidence with EUROBALL IV installed at the VIVITRON. Results on the population of specific structures of large deformation will be presented.

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Abstract: A core-excited Ipi = (12+) spin-gap isomer was identified in 98Cd in an experiment at EUROBALL IV. It was found to feed the known Ipi = (8+) seniority isomer by an E4 transition. Half-lives of T1/2 = 0.23(((+4)/(-3))) µs and 0.17(((+6)/(-4))) µs were measured for the two states at Ex = 6635 keV and 2428 keV, respectively. From the excitation energy of the core-excited isomer a 100Sn shell gap of 6.46(15) MeV is inferred. The measured E4 and E2 strengths, 100Sn core excitations and the origin of empirical polarization charges are discussed in the framework of large-scale shell model calculations. An E2 polarization charge for protons of deltaepi<0.4 e is found, which corresponds to the empirical value deltaepi = 0.45(((+20)/(-25))) e in the pure proton hole valence space.

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Abstract: The possible occurrence of highly deformed configurations is investigated in the <mi?N</mi? = <mi?Z</mi?nuclei 40Ca, 44Ti, and 56Ni as formed in the 28Si+12C, 16O+28Si, and 28Si+28Si reactions by using the properties of the emitted light charged particles (LCP). The energy spectra, in-plane and out-of-plane angular correlations of LCP's are analysed for each of the 3 studied reactions within the framework of the statistical model. Strong deformation effects are deduced from Hauser�Feshbach calculations performed with the Monte Carlo code CACARIZO by using a consistent set of parameters with spin-dependent level densities. The analysis of <mi?α</mi? particles in coincidence with 32S fragments emitted in 28Si+12C shows a strong contribution from a 8Be cluster emission. The binary nature of this cluster emission has been verified in three other reactions involving a 12C target: 27Al+12C, 31P+12C, and 32S+12C.

Abstract: Excitation functions for sub- and near-barrier total (complete + incomplete) fusion cross sections are presented for the 6,7Li+59Co reactions. Evaporation residues were identified by their characteristic γ rays and the corresponding yields measured with both the IReS Garel + array at the Vivitron facility and with the São Paulo Ge array at the 8UD Pelletron tandem facility using standard γ-ray techniques. The data extend to medium-mass systems previous works exploring the coupling effects (hindrance versus enhancement) in fusion reactions of both lighter and heavier systems. The results indicate a small enhancement of total fusion for the more weakly bound 6Li at sub-barrier energies, with similar cross sections for both reactions at and above the barrier.

Abstract: The complex fragments (or intermediate mass fragments) observed in the low-energy 58Ni + 58Ni �116Ba* reaction, are studied within the dynamical cluster-decay model for s-wave with the use of the temperature-dependent liquid drop, Coulomb and proximity energies. The important result is that, due to the temperature effects in liquid drop energy, the explicit preference for α-like fragments is washed out, though the 12C (or the complementary 104Sn) decay is still predicted to be one of the most probable α-nucleus decays for this reaction. The production rates for non-α-like intermediate mass fragments (IMFs) are now higher and the light-particle production is shown to accompany the IMFs at all incident energies, without involving any statistical evaporation process in the model. The comparisons between the experimental data and the (s-wave) calculations for IMF production cross sections are rather satisfactory and the contributions from other ell-waves need to be added for a further improvement of these comparisons and for calculations of the total kinetic energies of fragments.

Abstract: Total (complete+incomplete) fusion excitation functions of 6,7Li on 59Co and 209Bi targets around the Coulomb barrier are obtained using a new continuum discretized coupled channel method of calculating fusion. The relative importance of breakup and bound-state structure effects on total fusion is particularly investigated. The effect of breakup on fusion can be observed in the total fusion excitation function. The breakup enhances the total fusion at energies just around the barrier, whereas it hardly affects the total fusion at energies well above the barrier. The difference between the experimental total fusion cross sections for 6,7Li on 59Co is notably caused by breakup, but this is not the case for the 209Bi target.

Abstract: The decay of 56Ni*, formed in 32S+24Mg reaction at the incident energies Ec.m.=51.6 and 60.5 MeV (where c.m. is the center of mass), is calculated as a cluster decay process within the preformed cluster-decay model of Gupta et al. [Phys. Rev. C 65, 024601 (2002)] reformulated for hot compound systems. Interestingly enough, the cluster decay process is shown to contain the complete structure of both the measured fragment cross sections and total kinetic energies (TKEs). The observed deformed shapes of the exit channel fragments are simulated by introducing the neck-length parameter at the scission configuration, which nearly coincides with the 56Ni saddle configuration. This is the only parameter of the model, which, though, is also defined in terms of the binding energy of the hot compound system and the ground-state binding energies of the various emitted fragments. For the temperature effects included in shell corrections only, the normalized α-nucleus s-wave cross sections calculated for nuclear shapes with outgoing fragments separated within nuclear proximity limit (here �0.3 fm) can be compared with the experimental data, and the TKEs are found to be in reasonably good agreement with experiments for the angular momentum effects added in the sticking limit for the moment of inertia. The incident energy effects are also shown in predicting different separation distances and angular momentum values for the best fit. Also, some light particle production (other than the evaporation residue, not treated here) is predicted at these energies and, interestingly, 4He, which belongs to evaporation residue, is found missing as a dynamical cluster-decay fragment. Similar results are obtained for temperature effects included in all the terms of the potential energy. The non-α fragments are now equally important, and hence present a more realistic situation with respect to experiments.

Abstract: The effect of breakup in the fusion cross section in terms of suppression versus enhancement, discussed in a conflicting way in the literature is addressed. Data and theoretical predictions available in the literature are compared. Excitation functions of the sub- and near-barrier fusion cross-sections for a wide variety of light and heavy systems are presented and interpreted. We have measured fusion excitation functions and breakup correlation functions for the medium weight systems 6Li + 59Co and 7Li + 59Co. These measurements help to establish the influence of the projectile breakup on the fusion process at near-barrier energies and contribute to the determination of how the mass of the target affects the breakup role. The results indicate a light fusion enhancement at sub-barrier energies and a geometry dominated cross section at barrier energies.

Abstract: Highly excited and rapidly rotating compound nuclei (CN) produced in fusion-evaporation (FE) reactions can be well investigated by using charged particle spectroscopy. In such hot nuclei, with excitation energies as high as E*CN = 80 MeV, the spectral shapes of alpha particles provide information on the nuclear deformation. We report here on in-plane light charged particle (LCP) --- heavy-ion (HI) coincident measurements for the 16{O} + 28Si reaction. The experiment was carried out at three bombarding energies, Elab(16{O}) = 76, 96 and 112 MeV with the multidetector array ICARE at the VIVITRON Tandem facility. The Monte Carlo version of the statistical-model code CASCADE, which describes the FE process, has been used to characterize the 44Ti CN. A unique set of deformability parameters reproduces well the experimental alpha spectra to the three bombarding energies. The discrepancies observed for the proton spectra are still to be explained.

Abstract:

Abstract: The possible occurrence of highly deformed configurations in the 40Ca dinuclear system formed in the 28Si+12C reaction is investigated by analyzing the spectra of emitted light charged particles. Both inclusive and exclusive measurements of the heavy fragments (A>~10) and their associated light charged particles (protons and α particles) have been made at the IReS Strasbourg VIVITRON Tandem facility at bombarding energies of Elab(28Si)=112 MeV and 180 MeV by using the ICARE charged particle multidetector array. The energy spectra, velocity distributions, and both in-plane and out-of-plane angular correlations of light charged particles are compared to statistical-model calculations using a consistent set of parameters with spin-dependent level densities. The analysis suggests the onset of large nuclear deformation in 40Ca at high spin.

Abstract: Velocity and energy spectra of the light charged particles emitted in the 28Si(Elab=112�MeV)+28Si reaction have been measured at the Strasbourg VIVITRON Tandem facility. The ICARE charged particle multidetector array was used to obtain exclusive spectra of the protons and α particles in the angular range 15°�150° and to determine the angular correlations of these particles with respect to the emission angles of the evaporation residues. The experimental data are analyzed in the framework of the statistical model. The exclusive energy spectra of α particles emitted from the 28Si+28Si compound system are generally well reproduced by Monte Carlo calculations using spin-dependent level densities. This spin dependence approach suggests the onset of large nuclear deformation at high spin. A reanalysis of previous α-particle data from the 30Si+30Si compound system, using the same spin-dependent parametrization, is also presented in the framework of a general discussion of deformation effects in the ACN�60 mass region.

Abstract: The 132 MeV 16O + 58Ni reaction has been experimentally investigated by using coincident charged particle techniques. A closed-form theoretical approach, describing in a simple picture the non-equilibrium component and the evaporative one of the angular correlation between light particles and reaction residues emitted in a peripheral heavy-ion collision, is applied � in the hypotesis of a sequential process � to the (C,N,O)-α and (C,N,O)-p differential multiplicities for the 16O + 58Ni at 8.25 MeV/A deep inelastic collision. From this analysis some reaction mechanism information is deduced.

Abstract: The 16O+58Ni deep-inelastic collision has been investigated at Elab(16O)=132 MeV by using coincident charged particle techniques. Exclusive data of the projectilelike fragments (C, N, and O) and their associated light charged particles (protons and α particles) were collected in coincidence. The experiment has been performed at the IReS Strasbourg VIVITRON Tandem facility by using the icare charged particle multidetector array. The measured velocity diagrams and in-plane angular correlations have been analyzed by a semiclassical model that combines equilibrium and nonequilibrium processes of a deep-inelastic scattering reaction. Following the hypothesis of a sequential process, this closed-form theoretical approach is applied to the measured [(C,N,O)-p] and [(C,N,O)-α] differential multiplicities. Estimates on polarization phenomena and on �decay times� are used to provide information about deep-inelastic scattering in 16O+58Ni at 8.25 MeV/nucleon

Abstract: (96 MeV) 16O+58Ni and (133 MeV) 16O+48Ti reactions have been experimentally investigated by using coincident charged particle techniques. A closed-form theoretical approach, describing in a single picture the nonequilibrium component and the evaporation component of the angular correlation between particles and reaction residues emitted in a peripheral heavy-ion collision, is applied�in the hypothesis of sequential process�to the C-α, N-α, and O-α differential multiplicities for the 16O+58Ni at 6 MeV/nucleon and 16O+48Ti at 8.3 MeV/nucleon deep inelastic collisions. From this analysis some reaction mechanism information is deduced.

Abstract: Using particle-γ coincidences we have studied the population of final states after the emission of two α-particles and of 8Be in nuclei formed in 32S + 24Mg reactions at an energy of EL(32S) = 130 MeV. The data were obtained in a set-up consisting of the GASP γ-ray detection array and the multidetector array ISIS. Particle identification is obtained from the �E and E signals of the ISIS silicon detector telescopes, with the 8Be being identified by the instantaneous `pile up' of the �E and E pulses. γ-ray decays of the 48Cr nucleus are identified with coincidences set on two α-particles and on 8Be. Some transitions of the side-band with K� = 4- show a stronger population for 8Be emission relative to that of two α-particles (by a factor of 1.5-1.8). This observation is interpreted as being due to enhanced emission of 8Be into a more deformed nucleus. Calculations based on the extended Hauser-Feshbach compound decay formalism confirm this observation quantitatively.

Abstract: A high-resolution measurement of fragment-fragment-γ triple coincidence events in the symmetric and near-symmetric mass exit channels from the 28Si+28Si reaction has been undertaken using the EUROGAM Phase II γ-ray spectrometer. The bombarding energy of Elab(28Si)=111.6�MeV has been selected to populate the conjectured J�=38+ quasimolecular resonance in the 56Ni dinuclear system. In the 28Si+28Si symmetric mass exit channel, the resonance behavior is clearly verified at the chosen energy. The population of highly excited states in the 24Mg, 28Si, and 32S nuclei is discussed within a statistical fusion-fission model. Evidence is presented for selective population of states in the 28Si fragments arising from the symmetric fission of the 56Ni compound nucleus. The enhanced population of the K�=31- band of the 28Si nucleus, indicative of an oblate deformed shape, suggests that the oblate configuration plays a significant role in the resonant process. Fragment angular distributions for the elastic and low-lying inelastic channels as well as γ-ray angular correlations for the mutual inelastic channel (2+,2+) indicate that the spin orientations of the outgoing fragments are perpendicular to the orbital angular momentum. This unexpected result, which is different from the alignment found for the resonance structures in the 24Mg+24Mg and 12C +12C systems, suggests a situation where two oblate 28Si nuclei interact in an equator-to-equator stable molecular configuration. A discussion concerning the spin alignment and spin disalignment for different reactions such as 12C +12C, 24Mg+24Mg, and 28Si+28Si is presented.

Abstract: The possible occurrence of highly deformed configurations is investigated in the 40Ca and 56Ni di-nuclear systems as formed in the 28Si + 12C, 28Si reactions by using the properties of emitted light charged particles. Inclusive as well as exclusive data of the heavy fragments and their associated light charged particles have been collected by using the ICARE charged particle multidetector array. The data are analysed by Monte Carlo CASCADE statistical-model calculations using a consistent set of parameters with spin-dependent level densities. Significant deformation effects at high spin are observed as well as an unexpected large 8Be cluster emission of a binary nature.

Abstract: A first experiment was performed with the Binary Reaction trigger Spectrometer (BRS) for Euroball, as second last experiment of phase III. The reaction 24Mg(32S, 56Ni*) at E = 163.5 MeV was chosen in order to populate a specific hyperdeformed resonance state in the compound nucleus 56Ni* at E* = 84 MeV (J� = 46+) and to investigate the spectroscopy of its binary descendents. The experimental setup combined the γ-detector array Euroball III, without the phase I Ge detectors, the two large-area gas detector telescopes of the BRS at forward angles and 31 of the 40 detectors of the 4� silicon ball EUROSiB (now called ROSiB) at backward angles. We report on results of binary reaction triggers collected with one BRS telescope. Binary events are separated from evaporation residues due to (i) the large laboratory scattering angles of the detected reaction fragments, the opening angle of the BRS telescope being θ = 12 ° � 46 °, and (ii) by means of particle identification in the telescope. In this paper channels with emission of 8Be plus two protons and of 12C will be discussed.

Abstract: A review of the characteristic features found in fully energy-damped, binary decay yields from light heavy-ion reactions with 20�Atarget+Aprojectile�80 is presented. The different aspects of these yields that have been used to support models of compound-nucleus (CN) fission and deep-inelastic dinucleus orbiting are highlighted. Cross-section calculations based on the statistical phase space at different stages of the reaction are presented and compared to the experimental results. Although the statistical models are found to reproduce most of the observed experimental behaviors, an additional reaction component corresponding to a heavy-ion resonance or orbiting mechanism is also evident in certain systems. The system dependence of this second component is discussed. The extent to which the binary yields in very light systems (ACN�32) can be viewed as resulting from a fusion�fission mechanism is explored. A number of unresolved questions, such as whether the different observed behaviors reflect characteristically different reaction times, are discussed.

Abstract: The elastic scattering of 16O+16O has been measured at nine energies between Elab=75 and 124 MeV. The data cover up to 100° in the c.m. and can be described in terms of phenomenological and folding model potentials which reproduce the main features observed. In agreement with studies at higher energies in this and similar systems, refractive effects are present in the angular distributions at all energies. In particular, the passage of Airy minima through 90° at Ec.m.=40, 47.5, and 62 MeV explains the deep minima observed in the excitation function. The real part of the optical potential is found to vary very little with energy over the studied interval, but the imaginary part shows a rapid change in its shape at incident energy about 90 MeV. Nonetheless, the energy dependence of the volume integral of the real and imaginary parts is in agreement with dispersion relation predictions.

Abstract: Complete angular distributions of the 16O + 16O elastic channel have been measured at the 9 following bombarding energies: Elab = 75.0, 80.6, 87.2, 92.4, 94.8, 98.6, 103.1, 115.9 and 124 MeV using at forward angles (θlab = 5° to 20°) the Q3D spectrometer and at backward angles (θlab = 20° to 50°) two Position Sensitive Silicon detectors in kinematical coincidence. Refractive effects giving rise to nuclear rainbows and the associated Airy structures have been observed for this system. An optical model analysis has been done where the real part of the potential has been determined with no ambiguity over the whole energy range whereas the absorption (imaginary part) changed drastically around Elab = 90 MeV.

Abstract: Fragment-fragment-γ coincidences have been measured for 28Si+28Si at an energy corresponding to the population of a conjectured resonance in 56Ni. Fragment angular distributions as well as γ-ray angular correlations indicate that the spin orientations of the outgoing fragments are perpendicular to the orbital angular momentum. This differs from the 24Mg+24Mg and the 12C+12C resonances, and suggests two oblate 28Si nuclei interacting in an equator-to-equator molecular configuration.

Abstract: The results presented in this paper clearly suggest that a coherent framework may exist which connects the topics of heavy-ion molecular resonances, hyperdeformation effects, and fission shape isomerism. New data on particle-particle-gamma triple coincidences of the 28Si+28Si reaction at a beam energy corresponding to the population of a conjectured Jpi = 38+ resonance in 56Ni are presented. The absence of alignment of the spins of the outgoing fragments with respect to the orbital angular momentum is found to be in contrast with the alignment as measured for the 24Mg+24Mg resonances. A molecular-model picture is presented to suggest a ``butterfly'' motion of two oblate 28Si nuclei interacting in a equator-to-equator molecular configuration.

Abstract: The 12C+ 12C excitation functions have been studied for unbound inelastic channels at centre-of-mass energies between 35 and 45 MeV and for transfer channels between 30 and 60 MeV, in steps of 250 keV. Results are presented for the inelastic channels (0+1,0+2), (0+1,3-1) and (0+1,4+1) to the unbound 12C states above the alpha-particle decay threshold and for the one- and two-nucleon transfer channels. Intermediate-structure resonances tend to disappear above Ec.m. = 35 MeV, while a broad structure becomes a general feature of the interaction at higher energies.

Abstract: Inclusive as well as exclusive energy spectra of the light charged particles emitted in the 28Si(Elab = 112.6 MeV) + 28Si, 12C reactions have been measured at the Strasbourg VIVITRON facility in a wide angular range 150 � 1500, using the ICARE multidetector array. The observed α-particle energy spectra are generally well reproduced by the statistical model using a spin-dependent level density parameterisation. The results suggest significant deformation effects at high spin.

Abstract: Fusion-fission and fully energy-damped binary processes of the 35Cl+24Mg reaction were investigated using particle-particle coincidence techniques at a 35Cl bombarding energy of Elab , 8 MeV/nucleon. Inclusive data were also taken in order to determine the partial wave distribution of the fusion process. The fragment-fragment correlation data show that the majority of events arises from a binary-decay process with a relatively large multiplicity of secondary light-charged particles emitted by the two primary excited fragments in the exit channel. No evidence is observed for ternary-breakup processes, as expected from the systematics recently established for incident energies below 15 MeV/nucleon and for a large number of reactions. The binary-process results are compared with predictions of statistical-model calculations. The calculations were performed using the Hauser-Feshbach method, based on the available phase space at the scission point of the compound nucleus. This new method uses temperature-dependent level densities and its predictions are in good agreement with the presented experimental data, thus consistent with the fusion-fission origin of the binary fully-damped yields.

Abstract: Compound-nucleus fusion and binary-reaction mechanisms have been investigated for the 35Cl+24Mg system at an incident beam energy of Elab= 282 MeV. Charge distributions, inclusive energy spectra, and angular distributions have been obtained for the evaporation residues and the binary fragments. Angle-integrated cross sections have been determined for evaporation residues from both the complete and incomplete fusion mechanisms. Energy spectra for binary fragment channels near the entrance-channel mass partition are characterized by an inelastic contribution that is in addition to a fully energy damped component. The fully damped component which is observed in all the binary mass channels can be associated with decay times that are comparable to, or longer than, the rotation period. The observed mass-dependent cross sections for the fully damped component are well reproduced by the fission transition-state model, suggesting a fusion followed by fission origin. The present data cannot, however, rule out the possibility that a long-lived orbiting mechanism accounts for part or all of this yield.

Abstract: Binary-reaction channels of 19F+12C have been studied at Elab(19F)=92�MeV using kinematic coincidence techniques. The results are discussed in the light of previous inclusive measurements performed at the same incident energy and for which the occurrence of an important incomplete fusion mechanism after projectile breakup was proposed. Evidence for strong damped binary, especially quasisymmetric, decay processes is found.

Abstract: Single and multinucleon transfer yields for the 136Xe+64Ni reaction at a scattering energy �5% above the Coulomb barrier energy are studied using particle�γ-ray coincidence data. Q-value and scattering-angle distributions are extracted for the stronger channels. A fast transfer mechanism dominates the yields to these channels over an extended Q-value range, leading to a concentration of the cross section near the grazing angle. Analysis of the angular distributions based on a semiclassical barrier penetration model suggests that the single-nucleon and two-neutron exchange channels are dominated, respectively, by direct and two-step sequential transfer from the ground or low-lying excited states of the participating nuclei. The multiproton transfer channels have angular distributions that indicate a more complex mechanism, although direct cluster transfer from an excited configuration cannot be fully discounted. In a separate analysis, the relative population of different mass channels is found to be in general agreement with the expectations of a �random walk� model of particle exchange.

Abstract: A prominent and wide resonance centered at Ec.m.=32.5 MeV has recently been found in the (02+,02+) inelastic channel of the 12C+12C reaction. It has been suggested that it corresponds to a 6α-particle-chain state in 24Mg. In the present work we study 12C+12C excitation functions between center-of-mass energies of 30 and 35 MeV in steps of 250 keV for weakly populated outgoing channels. We present the inelastic channels to the states above the α-particle decay threshold, (01+,02+), (01+,31-), and (01+,41+), and the one- and two-nucleon transfer channels. In the inelastic and the transfer channels we observe correlated intermediate-width structures at Ec.m.=31, 32.5, and 33.5 MeV, whose widths are appreciably smaller than the width measured in the (02+,02+) channel. Our Ec.m.=32.5 MeV angular distribution of the (01+,02+) channel exhibits oscillatory behavior and, unlike that of the (02+,02+) channel, does not display enhancement around θc.m.=90°. Data were collected via the kinematic coincidence technique. For data reduction we use a novel approach allowing for the extraction of results on nonbinary channels.

Abstract: An extended Hauser-Feshbach method (EHFM) is developed for light heavy-ion fusion reactions in order to provide a detailed analysis of all the possible decay channels by including explicitly the fusion-fission phase space in the description of the cascade chain. The mass-asymmetric fission component is considered as a complex-fragment binary decay which can be treated in the same way as the light-particle evaporation from the compound nucleus in statistical-model calculations. The method of the phase-space integrations for the binary decay is an extension of the usual Hauser-Feshbach formalism to be applied to the mass-symmetric fission part. The EHFM calculations include ground-state binding energies and discrete levels in the low-excitation-energy regions which are essential for an accurate evaluation of the phase-space integrations of the complex-fragment emission (fission). In the present calculations, the EHFM is applied to the first-chance binary decay by assuming that the second-chance fission decay is negligible. In a similar manner to the description of the fusion-evaporation process, the usual cascade calculation of light-particle emission from the highly excited complex fragments is applied. This complete calculation is then defined as EHFM+cascade. Calculated quantities such as charge-, mass, and kinetic-energy distributions are compared with inclusive and/or exclusive data for the 32S+24Mg and 35Cl+12C reactions which have been selected as typical examples. Finally, the missing charge distributions extracted from exclusive measurements are also successfully compared with the EHFM+cascade predictions.

Abstract:

Abstract: The search and study of quasi-molecular resonances in the 31P composite system populated via two entrance channels are performed with two different experimental techniques. The 16O + 15N reaction products have been studied by the %-ray detection method at c.m. energies ranging from 15.5 MeV to 36.1 MeV. Binary channels of the 16O + 15N and 12C + 19F collisions have been studied by using the kinematical coincidence method at 26 incident energies ranging from Ec.m. = 20.6 MeV to 33.5 MeV for the first system, and at energies corresponding to the same excitation energies of the composite system for the second system. The 16O + 15N reaction exhibits two prominent gross structures in the large angle elastic scattering excitation function correlated with the resonant structures observed in inelastic channel %-ray yield measurements. Spin assignments were tentatively made for the two resonances. On the contrary, no such structures can be clearly established in the 12C + 19F system where only indications of non-correlated structures in various channels have been observed.

Abstract: Calculations for fission and cluster decay of 76Sr are presented for this nucleus to be in its ground state or formed as an excited compound system in heavy-ion reactions. The predicted mass distribution, for the dynamical collective mass transfer process assumed for fission of 76Sr, is clearly asymmetric, favoring α nuclei. Cluster decay is studied within a preformed cluster model, both for ground-state to ground-state decays and from excited compound system to the ground state(s) or excited states(s) of the fragments.

Abstract: Experimental data on strongly energy-damped yields from the 28Si+16O reaction at Ec.m.=39.1 and 50.5 MeV are analyzed in the context of fission from the 44Ti compound system. Several features of this system, including the presence of resonantlike structures in the elastic- and inelastic-scattering excitation functions, the observation of large cross sections for strongly damped yields, and the recognition that there are relatively few channels open for reactions involving the near-grazing partial waves, have been taken to infer a deep-inelastic as opposed to fission origin of the strongly damped yields. We test this claim by comparing the predictions of the transition-state model for fission to the experimental results. The statistical model is found to adequately describe the experimental results at the higher energy. The fully energy-damped inelastic yields at 39.1 MeV, however, are found to be far in excess of expectations based on the fission model. This result is in sharp contrast to what has been observed in the nearby 24Mg+16O system.

Abstract: The fully energy-damped yields for the 36Ar + 12C and 20Ne + 28Si reactions at Ec.m.=47.0 MeV and 45.5 MeV, respectively, are explored using particle-particle-γ coincidence data. These reactions reach a similar excitation energy of ECN*=59.5 MeV in the 48Cr compound nucleus as was obtained in an earlier particle-particle coincidence study of the 24Mg + 24Mg reaction. The overall mass and total kinetic energy distributions of the fission fragments are found to be well reproduced by statistical-model calculations. These calculations are also found to reproduce structure seen in the excitation-energy spectra for the 20Ne + 28Si and 24Mg + 24Mg exit channels for all three reactions. In previous excitation-function measurements, strong heavy-ion resonance behavior has been observed in elastic and inelastic cross sections for the 24Mg + 24Mg system. There has been speculation that peaks observed in the corresponding excitation-energy spectra at more negative Q values may also be a consequence of this resonance phenomenon. The observation of very similar behavior with the asymmetric-mass entrance channels makes it less likely, though, that the peaks arise from any special configuration of the compound system. Instead, an analysis of the γ-ray data and the results of statistical-model calculations support the conclusion that most of the observed high-lying structure can be accounted for in terms of statistical fission from a fully energy- and shape-equilibrated compound nucleus. For the 24Mg + 24Mg entrance channel, however, comparisons with the statistical model indicate a reduction of high-angular-momentum partial cross sections, leading to the 24Mg + 24Mg fission channel. For the first time, we are able to deduce the nature of the competition between the resonance and statistical-fission mechanisms in this mass region.

Abstract: The fully energy-damped yields from the 35Cl+12C reaction have been systematically investigated using particle-particle coincidence techniques at a 35Cl bombarding energy of �8 MeV/nucleon. The fragment-fragment correlation data show that the majority of events arises from a binary-decay process with rather large numbers of secondary light-charged particles emitted from the two excited exit fragments. No evidence is observed for ternary break-up events. The binary-process results of the present measurement, along with those of earlier, inclusive experimental data obtained at several lower bombarding energies are compared with predictions of two different kinds of statistical model calculations. These calculations are performed using the transition-state formalism and the extended Hauser-Feshbach method and are based on the available phase space at the saddle point and scission point of the compound nucleus, respectively. The methods give comparable predictions and are both in good agreement with the experimental results thus confirming the fusion-fission origin of the fully damped yields. The similarity of the predictions for the two models supports the claim that the scission point configuration is very close to that of the saddle point for the light 47V compound system. The results also give further support for the specific mass-asymmetry-dependent fission barriers needed in the transition-state calculation.

Abstract: The properties of the two-body channels in the 35Cl + 24Mg reaction at a bombarding energy of 275 MeV, have been investigated by using fragment-fragment coincident techniques. The exclusive data show that the majority of events arises from a binary-decay process. The rather large number of secondary light charged-particles emitted from the two excited exit fragments are consistent with the expectations of the Extended Hauser-Feshbach Method. Therefore no evidence for the occurence of ternary break-up events is observed.

Abstract: Global macroscopic features observed in the fully damped binary processes in light dinuclear systems, such as limiting angular momenta, mean total kinetic energies, and energy thresholds for fusion-fission processes (��fission thresholds��) are presented. Their deduced systematics are consistent with that obtained for heavier systems and follow a fusion-fission picture which can be described by a realistic rotating liquid drop model considering diffuse-surface and finite-nuclear-range effects.

Abstract: The entrance-channel mass-asymmetry dependence of the compound nucleus formation time in light heavy-ion reactions has been investigated within the framework of semiclassical dissipative collision models, The model calculations have been applied successfully to the formation of the Ar-38 compound nucleus as populated via the Be-9+Si-29, B-11+Al-27, C-12+Mg-26, and F-19+F-19 entrance channels. The shape evolution of several other light composite systems appears to be consistent with the so-called ''Fusion Inhibition Factor'' which has been observed experimentally. As found previously in more massive systems for the fusion-evaporation process, the entrance-channel mass-asymmetry degree of freedom appears to determine the competition between the different mechanisms as well as the time scales involved.

Abstract: t has been suggested that the resonance found at Ec.m.=32.5 MeV in an inelastic channel of 12C+12C corresponds to a six alpha-particle chain state. Reexamining our earlier data on this system a resonance is observed at the same energy in another outgoing channel, 16O+8Be, which is not expected to resonate for such a configuration. We observe similar angular distributions but an appreciably narrower width than that measured in the inelastic channel.

Abstract: The coexistence of quasi-molecular resonances, orbiting mechanisms and the fusion-fission (FF) process for medium light di-nuclear systems is examined in terms of the Number of Open Channels (NOC). The calculated NOC, based on a statistical model approach, shows a characteristic dependence which reflects the surface transparency needed to observe both resonant structure and orbiting phenomena. For more absorbing reactions FF has been found experimentally to compete with the fusion-evaporation (FE) process in agreement with larger predicted NOC values. Finally it shown that the coexistence of the statistical fission from the 48Cr compund nucleus (CN) and the resonances arising from very deformed configurations of this di-nucleus are well explained in the framework of the present simple model.

Abstract: The properties of binary fragments produced in the 35Cl+24Mg fusion reaction at a beam energy of ELab�8MeVA have been investigated by measurement of inclusive energy spectra, angular distributions and angular correlations between heavy fragments and evaporated charged particles. The fully damped components can be ascribed to a fusion-fission process.

Abstract: The properties of the two-body channels populated in the35Cl +12C reaction, at a bombarding energy of 180 KeV, have been studied by means of a kinematical coincidence technique. Binary reaction products show full energy equilibration and isotropic angular distributions in the center-of-mass frame. The asymmetrical elemental distribution of the fully-damped yields, similar to that observed previously in the32S +24Mg reaction, suggests the occurence of fusion-fission rather than orbiting.

Abstract: The occurrence of orbiting and fusion-fission processes observed experimentally in some light and medium-light heavy-ion collisions at incident energies well above the Coulomb barrier are discussed in the framework of a number of available open channels calculation. The fusion-fission mechanism appears to be less competitive in systems for which the available phase space for the highest partial waves is restricted to a few exit channels where dinuclear configurations can survive through orbiting trajectories. The coexistence of quasimolecular resonances, orbiting mechanisms, and the fusion-fission process for medium-light dinuclei is also briefly discussed

Abstract: Coincidences between light-charged particles and projectile-like fragments were measured at forward angles. An analysis of the data based on a kinematical reconstruction of the emitter evidences a thermalized emission for protons and a large non-equilibrium α emission. From the slope of the equilibrated component of the particle energy spectra in the emitter frame, high temperatures in the primary projectile, up to not, vert, similar4.5 MeV, have been extracted and are found to increase as the atomic number of the projectile-like fragment decreases.

Abstract: The light response of BaF2 crystals to light and heavy ions (1 � Z � 15) has been investigated as a function of energy, charge and mass of the incident particles up to not, vert, similar 40 A MeV. While it is possible to describe the light output using a unique function of E, Z and A for all the ions, the Birks' constant seems to depend on the charge of the incident ion. Only a small dependence on the mass of the detected ion is found.

Abstract: Fusion evaporation-residue cross sections for the 28Si+12C reaction have been measured in the energy range 18�Ec.m.�136 MeV using time-of-flight techniques. Velocity distributions of mass-identified reaction products were used to identify evaporation residues and to determine the complete-fusion cross sections at high energies. The data are in agreement with previously established systematics which indicate an entrance-channel mass-asymmetry dependence of the incomplete-fusion evaporation-residue process. The complete-fusion evaporation-residue cross sections and the deduced critical angular momenta are compared with earlier measurements and the predictions of existing models.

Abstract: The nuclear interaction probability of light charged particles in BaF2 crystals has been studied as a function of the incident particle energy. Light charged particles were identified in charge and mass by measuring their magnetic rigidity and their time-of-flight. The percentage of particles undergoing nuclear interactions has been measured for particles of charge from Z = 1 to Z = 6 and the experimental data are compared with the results of a model calculation.

Abstract: The properties of fully energy-damped processes (deep-inelastic orbiting, fusion-evaporation, and fusion-fission processes) have been investigated in the nearly mass-symmetric entrance-channel 23Na + 24Mg reaction leading to the 47V compound nucleus. By comparison with previous data for the mass-asymmetric 35Cl +12C reaction forming the same compound system at the same excitation energy, no entrance-channel effects are observed in either the evaporation residue or the fusion-fission yields. This is in contrast to the situation with the 28Si +12C and 24Mg +16O reactions where an orbiting process is evident. The asymmetrical elemental distributions of the fusion-fission fragments of the massA=47 system are well described by a transition-state model that accounts for the spin and mass-asymmetry dependence of the fission saddle point.

Abstract: Velocity distributions of mass-identified evaporation residues produced in the 28Si+40Ca reaction have been measured at bombarding energies of 309, 397, and 452 MeV using time-of-flight techniques. These distributions were used to identify evaporation residues and to separate the complete-fusion and incomplete-fusion components. Angular distributions and upper limits for the total evaporation-residue and complete-fusion evaporation-residue cross sections were extracted at all three bombarding energies. The complete-fusion evaporation-residue cross sections and the deduced critical angular momenta are compared with earlier measurements and the predictions of existing models. The ratios of the complete-fusion evaporation-residue cross section to the total evaporation-residue cross section, along with those measured for the 28Si+12C and 28Si+28Si systems at the same energies, support the entrance-channel mass-asymmetry dependence of the incomplete-fusion evaporation-residue process reported earlier.

Abstract: BaF2 crystals have been used as light charged particle detectors in the intermediate energy domain (20 < E/A < 100 MeV/nucleon) heavy ion reactions. Using shape discrimination in conjunction with time-of-flight measurements, good charge and mass separations have been achieved up to particles of charge Z = 3 and mass A = 7. The light response of the crystal to light charged particles is also investigated.

Abstract: Mass, velocity, and angular distributions have been measured for heavy products and for light charged particles from the reaction 215 MeV 16O+27Al. Coincidences between evaporation residues and light charged particles have also been measured. Statistical-model calculations, incorporating light-particle decay from either the compound nucleus or the composite nucleus formed in the direct emission of a beam velocity particle, cannot account for the observed cross sections or angular distributions of the heavy residues. More elaborate kinematic simulations, which include direct light-particle emission as observed in the light-particle inclusive data, also do not work. This supports the notion that heavy fragment production (A>4) would be needed to account for the residue distributions.

Abstract: The binary decay properties of the47V nucleus, produced in the35Cl +12C reaction, have been investigated at the35Cl bombarding energiesE lab = 180 and 200 MeV by means of a kinematical coincidence technique. Binary reaction products show full energy equilibration and a characteristic 1/sin(theta cm) angular distribution. The elemental distribution of the fully-damped products is asymmetric, similar to what has previously been observed in the decay of the56Ni nucleus. Comparison with theoretical model predictions suggests the occurrence of a fusion-fission rather than orbiting process. Moreover the calculations performed using the Extended Hauser-Feshbach Method reproduce well the experimental fission yields. A general discussion of orbiting and fusionfission experimental data of light heavy-ion systems is presented in the framework of the calculated number of available open channels for these systems.

Abstract: Excitation functions for12C+12C elastic and inelastic scattering to 2+ level have been measured over the energy range 30�60 MeV (cm) by 250 keV steps using the kinematical coincidence method. The intermediate structure resonances disappear aboveE cm=35 MeV while the broad and irregular structure becomes a general feature of the interaction at higher energies.

Abstract: The back-angle yields of the oxygen and carbon particles from the 31P+16O reaction have been measured at Elab(31P)=135.6 MeV by using reverse kinematics. Comparison with similar data for the 35Cl+12C reaction forming the same compound nucleus at the same excitation energy and with a very similar spin distribution shows very small entrance-channel dependence of back-angle yields. These results are in contrast to a similar study of the reactions 28Si+12C and 24Mg+16O. It is evident that the oxygen and carbon yields from the 31P+16O and 35Cl+12C reactions have a predominantly compound nucleus origin in contrast to those from the 28Si+12C and 24Mg+16O reactions. Possible connection of this nonequilibrium entrance channel dependence with the presence of nuclear molecular resonances is discussed.

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Abstract: Few-nucleon transfer reactions have been measured for the systems 64Ni+208Pb and 80Se+208Pb at energies slightly above the Coulomb barrier. Together with previous data, heavy-ion-induced transfer reactions on 208Pb have now been studied with projectiles in the mass range A=12�86. The experimental total reaction cross sections and the yields for quasielastic processes are compared with various theoretical predictions. For the one- and two-nucleon transfer reactions a systematic behavior of the energy- and angle-integrated cross sections is observed. This behavior can be understood within a simple semiclassical model. A comparison of the cross-section ratios between one- and two-neutron and the one- and the two-proton transfer reactions indicates that the two-proton-transfer process shows an enhancement with respect to the one-proton transfer reaction.

Abstract: Velocity distributions of mass-identified evaporation residues produced in the 28t/rSi+28Si reaction have been measured at bombarding energies of 174, 215, 240, 309, 397, and 452 MeV using time-of-flight techniques. These distributions were used to identify evaporation residues and to separate the complete-fusion and incomplete-fusion components. Angular distributions and total cross sections were extracted at all six bombarding energies. The complete-fusion evaporation-residue cross sections and the deduced critical angular momenta are compared with lower energy data and the predictions of existing models.

Abstract: We present data for small-angle particle-particle correlations from the reactions 80, 140, 215, and 250 MeV 16O+27Al�p-p or p-d. The main features of these data are anticorrelations for small relative momenta (�25 MeV/c) that strengthen with increasing bombarding energy. Statistical model calculations have been performed to predict the mean lifetimes for each step of evaporative decay, and then simulate the trajectories of the particle pairs and the resulting particle correlations. This simulation accounts very well for the trends of the data and can provide an important new test for the hypothesis of equilibration on which the model is built.

Abstract: The 13C+16O reaction has been studied by the kinematic coincidence technique in the Ec.m. range between 19 and 30 MeV. Angular distributions and excitation functions were compared with results from 12C+17O over the same energy range. Notable differences were found between the elastic angular distributions for the two reactions. Optical-model fits were performed to determine which parameters were sensitive to these differences. Broad structures, like shape resonances, were most apparent in the 13C+16O reaction, particularly for the excitation of collective states. Transfer reactions involving single-particle states show a more complex energy dependence.

Abstract: Fully energy-damped yields from the 32Mg reaction have been measured at center-of-mass energies of Ec.m.=51.6 and 60.5 MeV with the use of an experimental arrangement where both of the resulting heavy fragments could be detected in coincidence. Energy, velocity, and angular distributions of the reaction fragments have been determined. The cross sections prior to secondary light-particle emission have been deduced for the breakup of the compound system into different mass channels. These data are discussed in terms of two possible reaction mechanisms: fusion followed by fission and deep-inelastic orbiting.

Abstract: The properties of the two-body channels populated in the35Cl +12C reaction, at a bombarding energy of 180 KeV, have been studied by means of a kinematical coincidence technique. Binary reaction products show full energy equilibration and isotropic angular distributions in the center-of-mass frame. The asymmetrical elemental distribution of the fully-damped yields, similar to that observed previously in the32S +24Mg reaction, suggests the occurence of fusion-fission rather than orbiting.

Abstract: Mass and velocity distributions have been measured for the evaporation residue and fusion-fission products from the 16O+40Ca reaction at 214 MeV. Comparisons of Monte Carlo statistical evaporation simulations to the observed angle and mass dependences of the evaporation-residue velocity distributions were used to set limits on the maximum complete-fusion cross section and to extract information about the magnitude and character of incomplete-fusion processes. The extracted value of the complete fusion evaporation-residue cross section is discussed in the framework of previous results and existing models.

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Abstract: A large Bragg-curve spectrometer has been constructed and tested. The detector has a cylindrical geometry and operates with a homogeneous electric field. Energy resolutions of < 0.8% and Z resolutions of Z/�Z = 80 have been achieved for elastically scattered 58Ni ions. These results demonstrate the suitability of this large solid-angle detector for use in a wide variety of heavy-ion scattering experiments.

Abstract: Cross sections for the two-body channels populated in the 32S+24Mg reaction at Ec.m.=60.8 MeV have been measured by use of a coincidence technique which allows correction for secondary light-particle evaporation. The data show reaction yields with full equilibration of energy and mass-asymmetry coordinates. These results suggest an asymmetric fission mechanism and are contrary to what is expected from the previously proposed "orbiting" mechanism in light systems.

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Abstract: Binary channels of the 12C+ 17O reaction have been studied using a kinematic coincidence technique in the Ec.m. range 16.5 to 29.0 MeV. Angular distributions have been determined for the elastic, the inelastic to the first excited states of 17O and 12C, and the transfer channel to the ground states of 16O and 13C. The angular distributions for the inelastic scattering to the first excited state of 17O, which show strong oscillatory patterns over the whole energy range, could not be reproduced by distorted-wave Born approximation calculations. Structure is observed in the excitation functions of several channels. In particular the structure observed for the inelastic excitation of 17O is similar to that observed in previous γ-ray experiments.

Abstract: Excitation functions for the integrated yields of ten residual nuclei produced in the 12C + 17O and 13C + 16O reactions have been measured using γ-ray techniques and oxygen beams at bombarding energies from 20 to 70 MeV. In the case of the 12C + 17O reaction, the energy dependence of the strongest fusion channel cross sections is compared to evaporation model calculations. Compared to the 12C + 16O collision, the effect of the valence neutron is to strongly reduce the resonant behavior of the systems studied. The periodic structure observed in the inelastic channel to the first excited state of 17O is now established for both the 12C + 17O and 13C + 17O reactions. An explanation in terms of the Landau-Zener effect is suggested.

Abstract: Kinetic energy spectra, angular distributions, and elemental yield distributions have been measured for the 12 C + 16 O, 12 C + 18 O and 13 C + 17 O reaction products over an energy range from 2 to 7 times the Coulomb barrier energy. A careful kinematic analysis of the evaporation residues and comparisons with statistical-model calculations show that fusion proceeds with full momentum transfer followed by a statistical decay of the compound nucleus. The competition between complete fusion process and peripheral reactions in the 12 C + 16 O system is less important than for the 12 C + 18 O and 13 C + 17 O reactions. The unexpectedly high 12 C + 16 O complete fusion cross sections are related to the possible occurrence of a superdeformation of the 28 Si compound nucleus.

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Abstract: The evaporation residue yields have been measured for the 12C+16O reaction at five bombarding energies between 62 and 150 MeV. The important contributions of the fusion channels corresponding to 3α and 4α emission result in a total fusion cross section which saturates at higher energies and higher absolute value than previously reported. All observations are in favor of a complete fusion mechanism up to E(16O)=150 MeV.

Abstract: From angular correlation measurements with the 29Si(α, nγ) 32S reaction the 6 762-keV level has been assigned J� = 5-. Four new levels of 32S have been observed at Ex = 7 567-, 8 345-, 9 464- and 9 637-keV. The 7 567-keV level has been assigned J� = 5+ and the 8 345-keV level is a good candidate for the lowest 6+ state. The two higher levels are probably negative parity high spin states.

Abstract: Structure is observed in the yield curve for the 871-keV γ rays of 17O from the 13C + 17O reaction but absent for other observable transitions. The single-particle nature of the 17O transition suggests an interpretation in terms of the nuclear Landau-Zener effect.

Abstract: The 18O + 12C reaction has been studied from 20.0 to 32.4 MeV (c.m.) in steps of 200 keV. Twenty-one γ-ray excitation functions have been investigated, seven of them as binary, and fourteen as fusion-evaporation exit channels. Most of the excitation functions display structures which are strongly correlated. In particular, a one-to-one correspondence between the peaks of summed binary and summed fusion-evaporation excitation functions has been established. A comparison with the 14C + 16O system leading to the same 30Si composite nucleus is presented.

Abstract: The cross section for total fusion of the reaction 18O + 12C was studied over a large range of energies from near the Coulomb barrier BC to �6BC. Good agreement was found between the critical angular momenta deduced from the experimental results and the predictions of different models. The reaction 17O + 13C, leading to the same compound nucleus 30Si, was studied in the second fusion region (above �2BC). By comparing the relative cross sections for fusion-evaporation to each isotope it is shown that for different entrance channels, even at the highest energies studied, the reactions appear to pass by the formation of a compound nucleus. The critical angular momenta were found to be systematically different from 18O + 12C. This difference, which may be due partially to the entrance channel spin, is interpreted as arising from the effect of direct reactions diverting flux from the compound nuclear processes.

Abstract: The reaction channels of 14C + 14C have been studied from Ec.m.=12.5 to 32.5 MeV by γ-ray techniques. Correlated oscillatory structure has been observed in inelastic, transfer, and fusion-evaporation channels. These features are comparable to the behavior of 16O + 16O where similar dynamical conditions prevail.

Abstract: The yields of several nuclides produced in the 14C + 16O reaction have been measured over the range Ec.m=16-34 MeV. The excitation function for the production of 22Ne displays a regular sequence of narrow fine-structure resonances similar to those previously observed in the 12C + 16O reaction. This is the first time that such structure has been observed for systems of non-α-particle nuclei. Intermediate-width resonances are observed in the yield of 18O at Ec.m=19.5, 23.5, 27.5, and 31 MeV. Correlated structure appears in the inelastic scattering cross section to the 3- state of 14C at all these energies, except possibly Ec.m=19.5 MeV. The resemblance of the 23.5-MeV structure to anomalies previously observed in the 16O + 16O and 12C + 16O reactions is noted, and some properties of the compound system are deduced.

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Abstract: Carbon + carbon fusion-evaporation reactions have been studied in two series of measurements: (i) The system 13C + 13C has been studied for laboratoryy bombarding energies betwen 30 and 60 MeV in 5-MeV steps. Angular distributions for all residual nuclei have been measured and the corresponding yields versus bombarding energy are compared to a fusion-evaporation calculation. It is also shown that, at least at one bombarding energy, the fusion evaporation residue yields for the 12C + 14C and 13C + 13C systems are almost the same, confirming the independence of the way in which the compound nucleus 26Mg is formed. (ii) The systems 12C + 12C, 13C + 12C, 13C + 13C, and 13C + 14C have been studied at Elab=40 MeV. This energy corresponds approximately to the maxima of the fusion evaporation cross sections for all these systems. The yields to final residual nuclei show that the additional neutrons strongly affect mainly the αxn and 2αxn channels and this is well reproduced by the Hauser-Feshbach statistical model. The results are compared to those obtained for neighboring fusion-evaporation systems.

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Abstract: The radiative capture process of the 12C+12C and 12C+16O reactions has been studied using the very selective 0° Dragon spectrometer at Triumf and its associated BGO γ-array. The experiments have been performed at energies around the Coulomb barrier where resonances in the process have been reported. Our results show previously unobserved γ-decay to doorway states in the 24Mg and 28Si respectively around 10 to 12 MeV. The nature of the states is discussed and two scenarii are proposed.

Abstract: Charged particle and γ-decays in light α-like nuclei are investigated for 24Mg +12 C. Various theoretical predictions for the occurence of superdeformed and hyperdeformed bands associated with resonance structures with low spin are presented. The inverse kinematics reaction 24Mg +12 C is studied at Elab(24Mg) = 130 MeV. Exclusive data were collected with the Binary Reaction Spectrometer in coincidence with EUROBALL IV installed at the VIVITRON Tandem facility at Strasbourg. Specific structures with large deformation were selectively populated in binary reactions and their associated γ-decays studied. Coincident events from α-transfer channels were selected by choosing the excitation energy or the entry point via the two-body Q-values. The analysis of the binary reaction channels is presented with a particular emphasis on 20Ne-γ and 16O-γ coincidences.

Abstract: The influence on the fusion process of coupling transfer/breakup channels is investigated for the medium weight $^{6,7}$Li+$^{59}$Co systems in the vicinity of the Coulomb barrier. Coupling effects are discussed within a comparison of predictions of the Continuum Discretized Coupled-Channels model also applied to $^{6}$He+$^{59}$Co a reaction induced by the borromean halo nucleus $^{6}$He.

Abstract: The effect of breakup is investigated for the medium weight 6Li+59Co system in the vicinity of the Coulomb barrier. The strong coupling of breakup/transfer channels to fusion is discussed within a comparison of predictions of the Continuum Discretized Coupled-Channels model which is also applied to 6He+59Co a reaction induced by the borromean halo nucleus 6He.

Abstract: The heavy-ion radiative capture reactions 12C(12C,gamma)24Mg and 12C(16O,gamma)28Si have been performed on and off resonance at TRIUMF using the Dragon separator and its associated BGO array. The decay of the studied narrow resonances has been shown to proceed predominantly through quasi-bound doorway states which cluster and deformed configurations would have a large overlap with the entry resonance states. ©2006 American Institute of Physics

Abstract: It has been proposed to associate the narrow (Gamma=170 keV) and high spin (Jpi=36+) resonance in the 24Mg + 24Mg reaction at Ec.m= 45.7 MeV with a hyperdeformed molecular state in 48Cr. Such a description has important consequences for the resonance decay into the favoured inelastic channels. Through fragment-gamma coincidence measurements performed ON and OFF resonance using the PRISMA-CLARA array, we have established that the 24Mg states selectively populated are the 2+ and 4+ members of the ground state band. ©2006 American Institute of Physics

Abstract: The narrow (Gamma=170 keV) and high spin (Jpi=36+) resonance in the 24Mg + 24Mg reaction at ECM= 45.7 MeV has been associated with a hyperdeformed molecular state in 48Cr. Such a description has important consequences for the resonance decay into the favored inelastic channels. Through fragment-gamma coincidence measurements performed ON and OFF resonance using the PRISMA-CLARA array, we have identified the 24Mg states selectively populated: the 2+ and 4+ members of the ground state band.

Abstract: The study of $\gamma$-decays in $^{24}$Mg$^{*}$ is presented for excitation energies between the $\alpha$+$^{20}$Ne (9.3 MeV) and $^{12}$C+$^{12}$C (13.9 MeV) thresholds, where molecular resonances have been observed in $^{12}$C+$^{12}$C collisions. Various theoretical predictions exist for the occurence of superdeformed and hyperdeformed bands which can partially be identified with known resonance structures correlated in several reaction channels, and for which low spin members are predicted within the measured $^{24}$Mg$^{*}$ excitation energy region. The inverse kinematics reaction $^{24}$Mg$+^{12}$C has been investigated at E$_{lab}$($^{24}$Mg) = 130 MeV, an energy which enable the population of $^{24}$Mg states decaying into $^{12}$C+$^{12}$C resonant breakup states. Exclusive data were collected with the Binary Reaction Spetrometer (BRS) in coincidence with EUROBALL installed at the VIVITRON Tandem facility of the IReS at Strasbourg. Specific structures with large deformation were selectively populated in binary reactions and their $\gamma$-decays determined by using the BRS as a master trigger. Coincident events with inelastic as well as with binary $\alpha$-transfer channels have been selected by choosing the excitation energy or the entry point via the two-body Q-values. The analysis of the binary and quasi-binary reaction channels is presented with a particular emphasis on the $^{24}$Mg-$\gamma$ and $^{20}$Ne-$\gamma$ coincidences as well as the $^{12}$C-$^{12}$C coincidences.

Abstract: The gamma-decay of fragments from deep-inelastic and multi-nucleon transfer processes which occur when a beam of $^{26}$Mg at 160MeV is incident on a thin $^{150}$Nd target was studied using the EUROBALL IV array of escape suppressed Ge detectors at Strasbourg. The good resolving power of EUROBALL IV was further increased by combining it with the Binary Reaction Spectrometer (BRS), used for the detection of projectile-like fragments. The BRS allows full kinematic reconstruction of the binary reaction allowing crucial Doppler corrections of gamma-ray spectra to be performed. Some preliminary results are presented.

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Abstract: The possible occurence of highly deformed configurations is investigated in the $^{40}$Ca and $^{56}$Ni di-nuclear systems as formed in the $^{28}$Si + $^{12}$C and $^{28}$Si + $^{28}$Si reactions, respectively, by using the properties of emitted light charged particles. Inclusive as well as exclusive data of the heavy fragments (A $geq$ 6) and their associated light charged particles (p, d, t, and $alpha$-particles) have been collected at the IReS Strasbourg VIVITRON Tandem facility with two bombarding energies $E_{lab}(^{28}$Si) = 112 and 180 MeV by using the ICARE charged particle multidetector array, which consists of nearly 40 telescopes. The measured energy spectra, velocity distributions, in-plane and out-of-plane angular correlations are analysed by Monte Carlo CASCADE statistical-model calculations using a consistent set of parameters with spin-dependent level densities. Although significant deformation effects at high spin are needed, the remaining disagreement observed in the $^{28}$Si + $^{12}$C reaction for the S evaporation residue suggests an unexpected large unstable $^{8}$Be cluster emission of a binary nature.

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Abstract: Inclusive as well as exclusive energy spectra of the light charged particles emitted in the $^{28}$Si ($E_{lab}$=112.6 MeV) + $^{12}$C reaction has been measured using the {bf ICARE} multidetector array. The data have been analysed by statistical-model calculations using a spin-dependent level density parametrization. The results suggest significant deformation effects at high spin and cluster emission of $^8$Be.