Introduction

Abstract

The charge-exchange nuclear excitations for the isobars 48Ca → 48Sc, 90Zr → 90Nb and208Pb → 208Bi are considered in the framework of the theory of finite Fermi systems by exactly taking into account the particle-hole continuum.The distorted-wave impulse approximation (DWIA) is employed to calculate the angular distributions for the isobaric analogue states (IAS), Gamow-Teller resonances (GTR), dipole (L = 1, S = 0), spin-dipole (L = 1, S = 1), and so on, up to L = 7 excitations in the (p, n) reactions at bombarding proton energies Ep between 100 and 200 MeV. The results obtained are compared with experimental data and the conclusions concerning both the effective nucleon-nucleon interaction in the chargeexchange channel and the local quasiparticle charge eq[στ] with respect to the στ fields are discussed. It occurred that just below the GTR at small angles there is essentially no background from transitions with L > 0. It is shown that the theory describes fairly well the experimental data with the Landau-Migdal spin-isospin strength parameter g′ = 1.1 (G′ = 330 MeV · fm3) and eq[στ] = 0.8. The latter characterizes the quenching of the low-energy spin-isospin-flip transitions, i.e. the renormalization of the axial-vector vertices in nuclear matter.