• Energy Research
• Nuclear Physics A close

Abstract The new 4π multidetector INDRA, designed for the study of hot nuclear systems decaying by multifragmentation, is available for experiments since the beginning of 1993. First results emphasize its very high detection capabilities. Preliminary results on multiplicity distributions and elemental charge distributions in the most violent collisions for the 36 Ar+ 58 Ni and 129 Xe+ nat Sn systems are presented.

Abstract The 46, 48 Ti ( p , α) 43,45 Sc reaction has been studied at E p = 79.2 MeV. Differential cross sections and analyzing powers were measured for 12 levels in 43 Sc and 11 levels in 45 Sc. A striking j -transfer dependence is observed in the analyzing powers. The reaction is quite selective at this energy, populating the highest-spin states with the largest cross sections. DWBA calculations were performed for all states observed, and the results were found to represent the data for states of known J π quite well. Restrictions on the J π of a number of previously unidentified states were made. A semi-microscopic analysis, in which the form factors for the negative-parity states observed were derived from shell-model wave functions, produced fairly good agreement with the magnitudes of the cross sections for the known states, and resulted in further restrictions of possible J π for some levels.

Abstract One-nucleon and two-nucleon contributions to the unpolarized differential cross sections at 90° in the c.m. system are computed for the reactions 3,4 He(γ, p) 2, 3 H, for photon lab energies between 165 and 330 MeV. Experimental results from Saclay, being qualitatively different from earlier Frascati results, are supported by our calculations.

Abstract Recent experimental results on two-particle correlations measured in intermediate energy nucleus-nucleus collisions are reviewed. The emission and the sequential decay of particle unstable nuclei turn out to be an essential mechanism of the disintegration of nuclear systems. Consequences for single particle observables are discussed. In several experiments emission temperatures of about 5 MeV are found for 5 Li nuclei. These surprising observations are compared to fragment temperatures calculated with a statistical multifragmentation model.

Abstract We use measured isotopic yields of fragments produced in the reaction 40 Ar on 68 Zn at 27.6 MeV/nucleon in order to see whether these quantities may constitute a test which allows to gain some insight into the projectile fragmentation process. We compare the experimental distributions to those obtained with the multisequential decay model which we developed previously, the projectile break-up model proposed by Friedman and abrasion-ablation model calculations.

Abstract Recoil momenta of heavy spectators in intermediate-energy heavy-ion collisions of the order of 50–500 MeV per nucleon have been investigated within a statistical transfer model. Special emphasis was put on the role of fluctuations in defining the reaction geometry from correlation experiments involving recoil momenta and masses.

Abstract Optical-model analyses have been performed for the elastic scattering of antiprotons at 46.8 MeV from 12 C and at 180 MeV from 12 C, 40 Ca and 208 Pb. Calculations have also been performed with folded potentials and an effective antiproton-nucleon interaction has been derived. In the case of 12 C coupled channel effects due to the 2 + state at 4.43 MeV have been studied and deformation parameters in DWBA and in coupled channel calculations have been estimated for the vibrational as well as for the rotational model.

Abstract In intermediate energy heavy ion collisions, hot nuclear systems formed may disassemble by any of the three distinct mechanisms, namely, sequential fission, prompt multifragmentation or sequential evaporation. For identical multifragment channels considered for these three mechanisms, the correlation functions for intermediate mass fragments (IMFs) which are sensitive to the spatial-temporal extent of the emission process are exploited to delineate the different possible break-up scenarios.