Continuum angular distributions in preequilibrium nuclear reactions: Physical basis for Kalbach systematics.

Abstract

We show how momentum conservation is fundamental to the description of angular distributions in preequilibrium nuclear reactions. By using state densities with linear momentum to describe the phase space during the preequilibrium cascade, angular distributions can be derived in a transparent way. Fermi-motion and Pauli-blocking effects are included, and correlations between the emission particle's energy and angle are obtained for all orders of scattering. Our model provides a physical basis for many features of widely used phenomenological systematics of Kalbach, and provides a framework for understanding the systematical properties of continuum angular distributions.