Abstract
The new semimicroscopic model (particle-hole dispersive optical model) recently developed for de- scribing high-energy particle-hole-type excitations in medium-heavy mass nuclei is applied for the description of the simplest photonuclear reactions accompanied by excitation of the isovector giant dipole and quadrupole resonances. The calculated reaction cross sections and their derivatives are compared with corresponding experi- mental data and also with the similar results obtained within the previously developed semimicroscopic approach to the description of the giant resonances.
Highlights
The simplest photonuclear reactions (photoabsorption, direct+semidirect (DSD) photonucleon and inverse reactions) many years were a powerful tool of experimental studies of the isovector giant dipole and quadrupole resonances (IVGDR and IVGQR, respectively)
In case of giant resonances (GRs) in medium-heavy mass ’hard’ spherical nuclei these modes are: (i) particlehole (p-h) strength distribution, or Landau damping, which is a result of shell structure of nuclei; (ii) coupling of the (p-h)-type states, forming a given GR, to the single-particle (s. p.) continuum, that leads to GR direct-nucleon decay, or to the DSD reactions with one nucleon in the continuum; (iii) coupling of the mentioned (p-h)-type states to manyquasiparticle configurations, that leads to the spreading effect
These relaxation modes are taken into account within the semimicroscopic approach to the description of GRs (SMAGR) based on the versions of the continuum-Random-Phase-Approximation [2,3]
Summary
The simplest photonuclear reactions (photoabsorption, direct+semidirect (DSD) photonucleon and inverse reactions) many years were a powerful tool of experimental studies of the isovector giant dipole and quadrupole resonances (IVGDR and IVGQR, respectively) (see, e.g. [1]). (iii) coupling of the mentioned (p-h)-type states to manyquasiparticle configurations (chaotic states), that leads to the spreading effect These relaxation modes are taken into account within the semimicroscopic approach to the description of GRs (SMAGR) based on the versions of the continuum-Random-Phase-Approximation (cRPA) [2,3]. To formulate the cRPA equations in a closed form, these forces are taken as separable p-h dipole-dipole and quadrupole-quadrupole isovector velocity-dependent interactions (with the dimensionless intensities k0L , L = 1, 2) This extended version of the SMAGR is used in our recent paper [5], where reasonable description of the photoabsorption and the partial differential DSD (γ, n)− and (n, γ)−reaction cross sections is given for a number of medium-heavy mass spherical nuclei.
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