Choice of Nucleon-Nucleus Potential in the Calculation of Optical Potentials for Composite Projectiles

The disintegration effects for deuterons, tritons, and helions (${}_{}{}^3{}_{}{}^{}\mathrm{He}$) on their optical potentials are investigated in the framework of the adiabatic approximation. Using the eikonal approximation for the involved scattering amplitudes, it was possible to get analytic expression for the optical potentials of composite projectiles. The volume integrals of the resulting potentials are evaluated and compared with the corresponding quantities evaluated using the Watanabe model which neglects the disintegration of the projectiles. This comparison suggests that the disintegration of the projectile can be taken into account in the Watanabe model by an appropriate choice of the energy at which the nucleon potentials involved in the calculations are evaluated. An expression of this effective nucleon energy is given in terms of the volume integrals and mean square radii of the nucleon optical potentials. An extensive analysis of the energy and mass- number dependence of the phenomenological optical potentials of proton scattering at medium energies is given and used to evaluate the effective nucleon energy suggested in this work and to draw some conclusions on the validity of the extended optical model of Greenlees, Pyle, and Tang.