Expansion and evaporation of hot nuclei: Comparison between semi-classical and quantal mean-held approaches

We present a general discussion of the mean field dynamics of finite nuclei prepared under extreme conditions of temperature and pressure We compare the prediction of semi-classical approximation with complete quantum simulations. Many features of the dynamics are carefully studied such as the collective expansion, the evaporation process, the different time-scale, etc. This study points out many quantitative differences between quantum and semi-classical approaches. Part of the differences are related to numerical features inherent in semi-classical simulations but most of them are a direct consequence of the non-treatment of nuclei as quantal objects. In particular, we show that because of a too strong damping in semi-classical approaches the expansion of hot nuclei is quenched and the speed of the collective motion reduced. (C) 1998 Elsevier Science B.V.