Abstract
The recently proposed semi-microscopic approach, which consists in incorporating the “Coulomb description” of isospin-forbidden processes into the particle-hole dispersive optical model, is implemented to evaluate the main damping parameters of charge-exchange giant monopole resonances (including isobaric analog resonances) in medium-heavy spherical nuclei. The calculation results obtained for the 208Pb and 209Pb parent nuclei are compared with available experimental data.
Highlights
The problem in evaluating the main parameters of damping an arbitrary giant resonance consists in a necessity to describe together coupling the corresponding particlehole type states to the single-particle (s.-p.) continuum, and to many-quasiparticle configurations
The specific feature of high-energy charge-exchange monopole excitations is the presence of isobaric analog resonances (IARs), whose properties are closely related to approximate isospin-symmetry conservation in nuclei
In medium-heavy nuclei, the main mixing mechanism consists in IAR coupling to its overtone (the isovector monopole giant resonance in the β(−)channel, (IVMGR(−))) via a spatially variable part of the mean Coulomb field
Summary
The problem in evaluating the main parameters of damping an arbitrary giant resonance consists in a necessity to describe together coupling the corresponding particlehole type states to the single-particle (s.-p.) continuum, and to many-quasiparticle configurations (the spreading effect). The model is a microscopically-based extension of the standard and non-standard continuum-RPA (cRPA) versions on taking the spreading effect into account. In this semi-microscopic model, a mean field and the particlehole interaction responsible for long-range correlations are described microscopically, while the spreading effect is treated phenomenologically in terms of the strength of an energy-averaged particle-hole self-energy term. We extend this study and present the results of implementations of the semi-microscopic approach to a quantitative estimation of the main damping parameters for the above-mentioned IARs, and of the partial branching ratios for direct one-proton (one-neutron) decay of the IVMGR(−) (IVGMR(+)) based on the 208Pb parent-nucleus ground state (the IVMGR(+) is the isobaric partner of the IVMGR(−))
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