Asymmetric Fission ofNi56

Abstract

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

Publisher’s Note: Cluster decay of hot56Ni⋆formed in the32Gupta1, Kumar2, Dhiman3 et al. 2003Phys. Rev. CSelf Cite124330View full textAdd to dashboardCite

“…Note that 56 N i is a negative Q-value system (negative Q out , different for different exit channels) and hence would decay only if it were produced in heavy ion reactions with sufficient compound nucleus excitation energy E * CN (= E cm + Q in ), to compensate for the negative Q out , the deformation energy of fragments E d , their total kinetic energy TKE and the total excitation energy TXE, in the exit channel, as to the hot 56 N i * nucleus data from Refs. [2,3] in section 3. The (statistical) evaporation of light particles, that occur promptly before the beginning of the binary decay process of cluster emission studied here, is not included in this paper.…”

“…For the 32 S + 24 M g → 56 N i * reaction, in one of the experiments, the mass spectra for A=12 to 28 fragments and the total kinetic energy (TKE) for only the most favoured (enhanced yields) α-nucleus fragments are measured at the energies E lab = 121.1 and 141.8 MeV, or equivalently at E cm =51.6 and 60.5 MeV, respectively [2,3]. Note that 56 N i is a negative Q-value system (negative Q out , different for different exit channels) and hence would decay only if it were produced in heavy ion reactions with sufficient compound nucleus excitation energy E * CN (= E cm + Q in ), to compensate for the negative Q out , the deformation energy of fragments E d , their total kinetic energy TKE and the total excitation energy TXE, in the exit channel, as to the hot 56 N i * nucleus data from Refs.…”

“…Thus, the macroscopic liquid drop energy (V LDM ) is shown playing the most important role in the cluster decay calculations. Apparently, the compound nucleus being hot at the energies involved, the V LDM should also depend on the temperature T. This is done here in this paper for the decay of 56 N i * formed in 32 S + 24 M g reaction at the two energies, E cm =51.6 and 60.5 MeV [2,3]. Also, the other terms of the potential, that constitute the scattering potential V (R), are considered T-dependent.…”

“…The non-α fragments are now equally important and hence present a more realistic situation with respect to experiments. [2][3][4][5][6][7][8]). At such incident energies, the incident flux is found to get trapped by the formation of a compound nucleus (CN), which is in addition to a significant large-angle elastic scattering cross section.…”

Study of the fusion-fission process in the 35Cl +24Mg reaction

“…On the other hand reactions which produce three or more heavy fragments are known to be strongly suppressed in this energy regime. During the last two decades, considerable effort has been devoted to the understanding of the binary-reaction processes in heavy-ion collisions within the framework of a systematic study of the fusion-fission process (FF) for light-mass (20 ≤ A CN ≤ 60) composite systems [1][2][3][4][5][6][7][8][9][10][11][12][13]. It has been shown for example that entrance-channel effects do not play a significant role in the binary-decay processes of the 47 [7]) at comparable excitation energies and angular momenta.…”