Nuclear dissipation as damping of collective motion in the time-dependent RPA: (I). The microscopic model

Abstract

A microscopic model for describing nuclear dissipation as the damping of collective motion in the time-dependent RPA is considered. The collective state is defined as a solution of the RPA equations of motion in a restricted subspace, S 1, of discrete 1p-1h states. The damping of the collective motion is described by the time evolution of the wave packet which solves the time-dependent Schrödinger equation in an extended subspace, S, when initialized with the collective state. In the present paper we consider additional state of the 1p-1h structure only. The RPA solution for the wave packet describing the damping enables one to calculate — as a function of time — both the probability amplitude for finding the system in the collective state and the collective energy, and to extract their time decay under appropriate conditions. The rate of decrease of the collective energy is interpreted as the energy dissipation rate.