Surface effects and the spin-isospin nuclear response function.

Abstract

The response of the nuclear many body system to a spin-isospin dependent probe is investigated in the random phase approximation with the objective of studying the mechanism for the near equality of the transverse and longitudinal components of the spin response function observed in recent proton scattering experiments. We examine in particular the angular momentum dependence of R/sub L//R/sub T/ as a means to investigate the spatial origin of the various contributions to this ratio. The physical picture which emerges from our work suggests that two effects conjure themselves in producing R/sub L/--R/sub T/. At the nuclear surface probed by the proton beam, the smaller nuclear density reduces the effect of the difference between the longitudinal and transverse components of the particle-hole interaction. More importantly however, transverse-longitudinal mixing is also predominant at the nuclear surface producing altogether calculated values for R/sub L//sub X/R/sub T/ within the error bars of the experimental data.