Decay Rate of a Multidimensional System : Application to particle evaporation from a compound nucleus and fission(New Trends in Nuclear Collective Dynamics)

Abstract

I discuss two subjects concerning the decay of a metastable state in a system with many degrees of freedom. In the first part, I discuss the effect of a surface vibration of the residual nucleus on the energy spectrum of particles emitted from a hot compound nucleus. In the second part, I derive a formula of the fission width based on a path integral evaluation of the imaginary part of the free energy, and discuss how the Kramers formula is modified by the memory effect for viscosity and by the quantum fluctuation of the fission path. Attention is particularly paid to the effects of the finite range property of the coupling Hamiltonian between the fission coordinate and the environmantal degrees of freedom, which are represented by a set of harmonic oscillators. Also, I sketch the present understanding of the large enhancement of the heavy ion fusion cross section at sub-barrier energies.