Competition between the fusion-fission and deep-inelastic orbiting mechanisms in the35Cl +12C reaction

Abstract

The binary decay properties of the 477 nucleus, produced in the 35C1 + 12C reaction, have been investigated at the 35C1 bombarding energies Elab=180 and 200 MeV by means of a kinematical coincidence technique. Binary reaction products show full energy equilibration and a characteristic 1/sin(0om ) angular distribution. The elemental distribution of the fully-damped products is asymmetric, similar to what has previously been observed in the decay of the 56Ni nucleus. Comparison with theoretical model predictions suggests the occurrence of a fusion-fission rather than orbiting process. Moreover the calculations performed using the Extended HauserFeshbach 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.

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

“…bombarding energy in Fig.9 as first proposed by Winkler et al [37]. The two 35 Cl+ 12 C data points [6,24] and the point measured in this work for the 35 Cl+ 24 Mg reaction are shown as a full cross. The highest energy points (E lab ≈ 15…”

“…TSM predictions (dashed histograms) for Z ≤ 15 are not found to be as good as in the case of the EHFM+CASCADE calculations (full histograms). The TSM calculates too high FF cross sections due to a possible overestimation of the centrifugal potential [6]. One possible improvement would be the inclusion of the angular momentum dependent asymmetric fission barriers proposed by Sanders for light nuclei [4].…”

“…Further, transition-state model [1,4] calculations describe well the properties of the binary-decay channels and thus suggest a FF origin. The occurrence of FF rather than orbiting in certain light-mass systems has been the subject of large number of discussions [1,[4][5][6][7]13,14]. These have led, in most cases, to the conclusion [1] that FF has to be taken into account when exploring the limitations of the complete fusion (CF) process at large angular momenta and high excitation energies.…”

“…Nevertheless, the properties of the primary fission fragments can be deduced, even at energies as high as 275 MeV, by using the coincident data. As found for the 35 Cl+ 12 C reaction at the same incident energy [24] and at lower energies studied [3,6] The energy calibrations of the IC's were obtained using elastically scattered 35 Cl projectiles from 100 µg/cm 2 thick Au and C targets and from the Mg target, combined with measurements of α sources and a calibration pulser. On an event-by-event basis, corrections were applied for energy loss in the targets and in the entrance window foils on the IC's and for the pulse height defect in the Si detectors [30].…”

“…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.…”