Feshbach-Kerman-Koonin model analysis of preequilibrium (p,p') and (p,n) reactions at 12 to 26 MeV.

Abstract

Double-differential proton emission cross sections have been measured for proton-induced reactions on [sup 98]Mo and [sup 106]Pd at incident energies around 26 MeV. Several sets of ([ital p],[ital p][prime]) and ([ital p],[ital n]) data for both target nuclei at incident energies from 12 to 26 MeV are analyzed in terms of the multistep-direct (MSD) and multistep-compound (MSC) reaction models of Feshbach, Kerman, and Koonin (FKK). The strength [ital V][sub 0] of the effective [ital N]-[ital N] interaction is extracted from a fit of the calculated MSD spectrum to the experimental data using the subtraction method of isolating and analyzing the MSD component alone. A similar analysis is also applied to ([ital p],[ital p][prime]) and ([ital n],[ital n][prime]) data for [sup 93]Nb in the same energy region. The experimental nucleon emission spectra at 26 MeV are reproduced well by the calculation that includes preequilibrium MSD and MSC emission, direct collective excitation to low-lying discrete levels, and Hauser-Feshbach equilibrium emission in a quantum-mechanical way. The systematic dependence of [ital V][sub 0] on the incident energy and the nature of projectiles and ejectiles is investigated. In addition, the sensitivities to input parameters used in the MSD calculation (the optical model potential parameters, themore » pairing correction, and the nonlocality correction) are examined in order to see their effect on the determination of [ital V][sub 0]. The possibility of gradual absorption of reaction flux from the [ital P] to the [ital Q] chain is also discussed through analyses of preequilibrium ([ital p],[ital p][prime]) and ([ital p],[ital n]) spectra using a phenomenological phase space approach.« less