Internal excitation of intermediate mass fragments from collisions of 36Ar+Ag nuclei at 35 MeV/nucleon.

Abstract

Population rates for neutron-unbound states compared to bound states were determined for intermediate mass fragments from $^{36}\mathrm{Ar}$+Ag collisions at 35 MeV/nucleon. The population ratios were measured as a function of fragment kinetic energy at angles of 15\ifmmode^\circ\else\textdegree\fi{}, 30\ifmmode^\circ\else\textdegree\fi{}, 45\ifmmode^\circ\else\textdegree\fi{}, and 60\ifmmode^\circ\else\textdegree\fi{}, especially for $^{12}\mathrm{B}$ fragments but also for $^{7}\mathrm{Li}$, $^{8}\mathrm{Li}$, $^{11}\mathrm{Be}$, and $^{13}\mathrm{C}$ fragments. The results show no major dependence on either the kinetic energy or the emission angle of the fragments. There are signs of a moderate contribution to the dominating statistical decay from nonequilibrium quasi-elastic decay at the smaller angles. The population ratios for the different fragments are consistent with emission from a source of a single temperature which emits complex nuclei at freeze-out. Comparison of the present results with those from a similar experiment, but with $^{14}\mathrm{N}$ projectiles at 35 MeV/nucleon, shows that the population ratios for strongly damped processes are the same for both $^{14}\mathrm{N}$ and $^{36}\mathrm{Ar}$ projectiles on Ag.