Entrance-channel mass-asymmetry dependence of compound nucleus formation time in light heavy-ion reactions

The entrance-channel mass-asymmetry dependence of the compound nucleus formation time in light heavy-ion reactions has been investigated within the framework of semiclassical dissipative collision models. The model calculations have been applied successfully to the formation of the ${}_{}{}^{38}{}_{}{}^{}\mathrm{Ar}$ compound nucleus as populated via the ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$${+}^{29}$Si, ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$${+}^{27}$Al, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{26}$Mg, and ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$${+}^{19}$F entrance channels. The shape evolution of several other light composite systems appears to be consistent with the so-called ‘‘Fusion Inhibition Factor’’ which has been observed experimentally. As found previously in more massive systems for the fusion-evaporation process, the entrance-channel mass-asymmetry degree of freedom appears to determine the competition between the different mechanisms as well as the time scales involved. © 1996 The American Physical Society.