Dissipation of angular momentum in light heavy-ion collision

Abstract

The inclusive energy distributions of fragments $(4\ensuremath{\leqslant}Z\ensuremath{\leqslant}7)$ emitted in the reactions $^{16}\mathrm{O}(116\phantom{\rule{0.3em}{0ex}}\text{MeV})+^{27}\mathrm{Al}$, $^{28}\mathrm{Si}$, $^{20}\mathrm{Ne}(145\phantom{\rule{0.3em}{0ex}}\text{MeV})+^{27}\mathrm{Al}$, $^{59}\mathrm{Co}$ have been measured in the angular range ${\ensuremath{\theta}}_{lab}=10\ifmmode^\circ\else\textdegree\fi{}--65\ifmmode^\circ\else\textdegree\fi{}$. The respective fusion-fission and deep inelastic contributions have been decomposed from the experimental fragment energy spectra. The angular momentum dissipations in fully damped deep inelastic collisions have been estimated assuming exit channel configuration similar to those for fusion-fission process. It has been found that, the angular momentum dissipations are more than those predicted by the empirical sticking limit in all cases. The deviation is found to increase with increasing charge transfer (lighter fragments). Qualitatively, this may be due to stronger friction in the exit channel. Moreover, for the heavier system $^{20}\mathrm{Ne}+^{59}\mathrm{Co}$, the overall magnitude of deviation is less as compared to those for the lighter systems, i.e., $^{16}\mathrm{O}+^{27}\mathrm{Al}$, $^{28}\mathrm{Si}$, $^{20}\mathrm{Ne}+^{27}\mathrm{Al}$. This may be due to lesser overlap in time scales of fusion and deep inelastic time scales for heavier systems.