Abstract
Optical model studies of medium energy alpha particles and high energy pions using the microscopic model, are carried out to investigate the nuclear matter distribution. For medium energy alpha particles, the optical potentials are obtained by folding an effective alpha-nucleon interaction into the nuclear matter distributions which are constructed from single particle wave functions, and elastic scattering of alpha particles at 42 MeV is calculated. It is shown that the nuclear matter distributions obtained as above can explain reasonably well experimental data, if a suitable form for the effective interaction is chosen. Further, the ability of the microscopic model to reproduce the observed behaviour of the strong absorption radii, is examined and it is found that the strong absorption radii obtained, show systematic A-dependence. But it is noted that the small uncertainties in the range parameter of the effective interaction become significant when one is concerned with the precise behaviour of these radii. The same uncertainties also limit the accurate determination of the nuclear matter distribution. For high energy pions, the optical potentials are obtained by folding the free pion-nucleon interaction in momentum space into the nucleon form factors which are calculated using neutron and proton distributions obtained as before. Using these pion optical potentials, the Klein-Gordon equation is solved numerically and the absorption and differential cross-sections at energies in the region 0.585-1.057 GeV are calculated. These calculations are carried out using the complete expression for the pion-nucleon interaction as well as the large A approximation. It is shown that the absorption and differential cross-sections for light and medium mass nuclei are quite sensitive to the variations in the parameters of the pion optical potential and in particular, at the minima in the differential cross-sections, significant changes are produced. From a comparison of our results for the absorption cross-sections for such nuclei with some available experimental data, it is indicated that the use of the large A approximation may significantly alter the conclusions reached before about the nuclear matter distributions. It also appears that even for heavy nuclei, the use of this approximation is probably suspect, especially when one is concerned with the analysis of accurate experimental data.