Microscopic DWIA analysis of the (p, n) reactions

Abstract

Abstract The charge-exchange nuclear excitations for the isobars 48 Ca → 48 Sc , 90 Zr → 90 Nb and 208 Pb → 208 Bi 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 E p 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 e q [ 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 · fm 3 ) and e q [ 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.