STUDY OF THE GAMOW-TELLER RESONANCE IN NB-90 AND BI-208

An approach is proposed for studying the spreading properties of the G amow-Teller resonance (GTR) in heavy nuclei including the coupling to 2p2h configurations and the ground-state correlations beyond RPA. The GTR is generated by a proton p-neutron h (pi p-nu h) phonon within the renormalized RPA. The second-order configuration mixing beyond RPA is realized by constructing two-phonon configurations, in which one of t wo intermediate phonon states is a pi p-nu h phonon. The numerical cal culations are performed in the parent nuclei Zr-90 and Pb-208 making u se of M3Y nucleon-nucleon interaction and the single-particle wave fun ctions obtained in the standard harmonic oscillator potential, The sin gle-particle energies around the Fermi surface are substituted with th e empirical values or those given by a Woods-Saxon potential. The resu lts obtained provide a reasonable account for recent experimental find ings on the GTR in these nuclei. The extension of the present approach to highly excited (hot) nuclei is also provided. The GTR is found to be stable against temperatures up to T = 6 MeV. (C) 1997 Elsevier Scie nce B.V.