Semiclassical Treatment of Direct Nuclear Reactions

Abstract

A semiclassical method is employed to discuss the angular distributions of direct nuclear reactions. The method considers the incident and outgoing particles to be described by rays which follow classical paths; these rays can be refracted, reflected, and absorbed by a "clouded-crystal-ball" nucleus. Any given incident ray is considered to have a certain probability of suffering a major "scattering" at each point within a nucleus, this "scattering" not only changing the direction of the ray but also its wavelength. A condition of angular momentum conservation is imposed on this direct-scattering event, such that the angular momentum change in this process is equal to that required by the direct reaction under consideration.On this picture it is seen that the oscillations in the angular distributions which often occur with direct reactions arise as a result of interference between direct scatterings in different regions of the nucleus. Thus these oscillations are to be likened to the interference maxima and minima which arise when light is scattered, for example from a soap film. Effects due to compound nucleus absorption and of refraction and reflection of the incident and outgoing rays can be discussed fairly simply on this model.An investigation of the basis of the semiclassical method indicates that it should be reliable over a wide range of interesting conditions.