Effective Coupling Constants for Spin-Flip and Non Spin-Flip E1 Transitions in A∼90 Nuclei

Abstract

Radiative proton capture reactions through two isobaric analogue resonances (IAR) in 89 Y were studied, one was the 12.07 MeV 2d 5/2 state lying just above the neutron threshold energy B n and another was the 14.48 MeV 2d 3/2 state lying well above B n . E1 transitions from these IAR's were studied for favoured cases with no spin-flip and no change of radial nodes, and for unfavoured cases spin-flip and/or change of radial nodes. At the 2d 3/2 IAR lying well above B n , the favoured transitions show the resonance feature, but the unfavoured ones not. At the 2d 5/2 IAR near B n , however, both the favoured and unfavoured transitions show the resonance feature. Anormalous resonant feature of the unfavoured transitions is interpreted mainly due to the compound process. Favoured transitions are all found to be reduced by factors ∼0.3 over the shell model values.