Transition density of charge-exchange processes

Abstract

The transition density between parent and analog states is studied with an eye on its role in charge-exchange nuclear reactions. The structure of the target nucleus is described in a perturbative approach, in which the Coulomb and asymmetry potentials mix the eigenstates of a charge-independent single-particle Hamiltonian. In this model formulae are derived for the transition density, the Coulomb displacement energy, and the neutron-proton density difference, and their relationship is used to estimate the transition density. This estimate shows that (i) the largest contribution comes from the density of the excess neutrons; (ii) the weight of the Coulomb-mixing effect is small up to excess neutron number 10, and grows rapidly beyond; (iii) the weight of the core polarization term induced by the excess neutrons is modest and is the same for all nuclei. It is indicated that the Coulomb effect may explain the departure from the Lane model of nucleon charge-exchange scattering found for heavy nuclei, whereas the core polarization may account for the observed anomalous dependence of the 0/sup 0/ pion charge-exchange cross section on the number of excess neutrons.