Particle-hole Dispersive Optical Model Research Articles

Properties of Gamow-Teller and charge-exchange giant spin-monopole resonances in medium-heavy closed-shell parent nuclei: A semimicroscopic description

The basic version of the semimicroscopic particle-hole dispersive optical model is adopted and implemented to describe main properties of the Gamow-Teller and charge-exchange giant spin-monopole resonances in medium-heavy closed-shell parent nuclei. Calculation results obtained for $^{48}\mathrm{Ca}, ^{90}\mathrm{Zr}, ^{132}\mathrm{Sn}$, and $^{208}\mathrm{Pb}$ are compared with available experimental data.

Properties of isoscalar giant multipole resonances in medium-heavy closed-shell nuclei: A semimicroscopic description

The semimicroscopic particle-hole dispersive optical model (PHDOM) is implemented to describe main properties of Isoscalar Giant Multipole Resonances (up to L=3) in medium-heavy closed-shell nuclei. The main properties are characterized by the strength distribution, transition density, partial and total probabilities of direct one-nucleon decay. Calculation results obtained for the 208Pb nucleus are compared with available experimental data.

Semimicroscopic Description of High-Energy Charge-Exchange Spin-Monopole Excitations in Medium-Heavy Spherical Nuclei

The semimicroscopic particle–hole dispersive optical model developed recently is applied to describing main properties of the Gamow–Teller and charge-exchange giant spin-monopole resonances in medium-heavy closed-shell nuclei. The description in question includes energy-averaged strength functions, projected transition densities, and partial branching ratios for direct single-nucleon decay. By way of example, this approach is implemented for the $${}^{208}$$ Pb parent nucleus. The results of respective calculations are compared with available experimental data.

Semimicroscopic Description of Isoscalar Giant Multipole Resonances in the $${}^{\mathbf{208}}$$Pb Nucleus

An approach to describing main properties of isoscalar giant multipole resonances in medium-heavy closed-shell nuclei is proposed within the particle–hole dispersive optical model formulated recently. The description includes the energy-averaged strength function, projected transition density, and partial branching ratios for direct single-nucleon decay. The results obtained within this approach for the $${}^{208}$$ Pb nucleus are compared with available experimental data.

Coulomb Description of High-Energy Charge-Exchange Monopole Excitations in Medium-Heavy Spherical Nuclei

The recently proposed approach to the description of high-energy charge-exchange monopole excitations in medium-heavy spherical nuclei is implemented to quantitatively estimate the main damping parameters of the related giant resonances including the isobaric analog resonance. The approach consists in incorporating the “Coulomb description” of isospin-forbidden processes into the particle-hole dispersive optical model. The results obtained for a few parent nuclei with $$Z = 50$$ and $$Z = 82$$ are compared with the respective experimental data.

Direct + Semidirect E1 Photoneutron Reactions: Semimicroscopic Description

The particle-hole dispersive optical model is implemented to describe together E1 photo-absorption and direct + semidirect photoneutron reactions accompanied by excitation of the giant dipole resonance. Being based on this description, a quantitative estimation of the partial and total branching ratios for direct one-neutron decay of the mentioned giant resonance in a few medium-heavy neutron-closed-shell nuclei is obtained. Calculation results are compared with corresponding experimental data.

On the spreading width of isobaric analog resonances

A description of the spreading width of the Isobaric Analog Resonances in medium-heavy mass spherical nuclei is proposed within a combined approach. This latter consists in incorporating the "Coulomb description" of isospin-forbidden processes into the newly developed particle-hole dispersive optical model. Within this approach, the observed spreading width of the resonances based on the 208,209Pb parent-nuclei ground state is quantitatively estimated without the use of specific adjustable parameters.

On unitarity of the particle–hole dispersive optical model

For the recently developed particle–hole dispersive optical model, weak violations of unitarity due to a phenomenological description of the spreading effect are considered. Methods for unitarity restoration are proposed and implemented for the 208Pb nucleus in the description of the energy-averaged isoscalar monopole double transition density and strength functions in a wide excitation energy interval that includes the isoscalar giant monopole resonance and its overtone. To illustrate abilities of the model, direct neutron decay of the mentioned giant resonance is also considered.

Damping parameters of charge-exchange giant monopole resonances within a semi-microscopic approach

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.

Damping of simple modes of high-energy nuclear excitations: dispersive optical models and their implementations

The particle-hole dispersive optical model, proposed recently to describe the main properties of high-energy particle-hole-type excitations in medium-heavy mass spherical nuclei, is briefly presented. Unique features of the model, new developments and some implementations are discussed. In applying to the description of deep-hole states, an unitary version of the single-quasiparticle optical model is also briefly presented.

On direct one-neutron decay of the giant dipole resonance

The newly developed particle-hole dispersive optical model is implemented to evaluate the partial and total branching ratios for direct one-neutron decay of the giant dipole resonance in a few neutron-closedshell nuclei. The calculation results obtained for 48Ca, 90Zr, 140Ce and 208Pb with no specific model parameters are compared with available experimental data.

Unitary version of the particle–hole dispersive optical model

For the particle–hole dispersive optical model developed recently, a method is proposed for restoring unitarity weakly violated by a phenomenological description of the spreading effect. The method is implemented by performing a quantitative analysis of the energy-averaged isoscalar monopole double transition density and strength functions over a broad energy range including the isoscalar giant monopole resonance and its overtone in the 208Pb nucleus.

Investigation of the energy-averaged double transition density of isoscalar monopole excitations in medium-heavy mass spherical nuclei

The particle–hole dispersive optical model, developed recently, is applied to study properties of high-energy isoscalar monopole excitations in medium-heavy mass spherical nuclei. The energy-averaged strength functions of the isoscalar giant monopole resonance and its overtone in 208Pb are analyzed. In particular, we analyze the energy-averaged isoscalar monopole double transition density, the key quantity in the description of the hadron–nucleus inelastic scattering, and studied the validity of the factorization approximation using semi classical and microscopic one body transition densities, respectively, in calculating the cross sections for the excitation of isoscalar giant resonances by inelastic alpha scattering.

On the excitation energy of deep-hole states in medium-heavy-mass spherical nuclei

Within the particle-hole dispersive optical model it is shown that the spreading effect determines a significant part of the anomalously large excitation energy of deep-hole states in the 90 Zr and 208 Pb parent nuclei.

Properties of isoscalar monopole particle-hole-type excitations in208Pb

The particle-hole dispersive optical model developed recently is applied to describe properties of high-energy isoscalar monopole excitations in 208 Pb. We consider, in particular, the double transition density averaged over the energy of the isoscalar monopole excitations in a wide energy interval, which includes the isoscalar giant monopole resonance and its overtone. The energy-averaged strength functions of these resonances are also analyzed. Some corrections to the calculation scheme are formulated to restore the model unitarity.

Properties of high-energy isoscalar monopole excitations in medium-heavy mass spherical nuclei

The recently developed particle-hole dispersive optical model is applied to describe properties of high-energy isoscalar monopole excitations in medium-heavy mass spherical nuclei. In particular, the double transition density averaged over the energy of the isoscalar monopole excitations is considered for 208Pb in a wide energy interval, which includes the isoscalar giant monopole resonance and its overtone. The energy-averaged strength functions of these resonances are also analyzed.

Description of the simplest photonuclear reactions within the particle-hole dispersive optical model

A recently developed particle-hole dispersive optical model is applied to describe the cross sections of photoabsorption, $\text{direct}+\text{semidirect}$ photoneutron and inverse reactions accompanied by excitation of the isovector giant dipole and quadrupole resonances in medium--heavy-mass spherical nuclei. The model is an extension of the standard and nonstandard versions of the continuum-random-phase approximation by including the spreading effect in a phenomenological way. It contains the following ingredients: the Landau--Migdal particle-hole interaction and a phenomenological mean field consistent with this interaction, isovector velocity-dependent forces taken in the simplest form and the imaginary part of an effective single-particle optical-model potential determining the corresponding dispersive part. All the model parameters are taken from the other data and from the description of photoabsorption, while the $\text{direct}+\text{semidirect}$ photoneutron and inverse reactions are described without the use of specific adjustable parameters. Calculation results obtained for a few neutron-closed-shell nuclei are compared with the corresponding experimental data.

Damping of high-energy particle-hole-type nuclear excitations: A semimicroscopic model

A semimicroscopic model (particle-hole dispersive optical model) is formulated to describe the main relaxation modes of high-energy particle-hole-type excitations in medium-heavy mass nuclei. Within this model, Landau damping and the single-particle continuum are considered microscopically, while the spreading effect is treated phenomenologically, employing a statistical assumption. Description of direct nucleon decay of the above-mentioned excitations (including giant resonances) is a unique feature of the proposed model, which in applying to closed-shell nuclei is arranged for practical implementations. The methodical similarity of formulations of the single-quasiparticle and particle-hole optical models is emphasized.

Damping of high-energy particle-hole-type nuclear excitations: a semi-microscopic model

A semi-microscopic model (particle-hole dispersive optical model) is formulated to describe the main relaxation modes of high-energy particle-hole-type excitations in medium-heavy mass nuclei. Within this model Landau damping and the single-particle continuum are considered microscopically, while the spreading effect is treated phenomenologically with taking a statistical assumption into account. Description of direct-nucleon-decay properties of the above-mentioned excitations (including giant resonances) is a unique feature of the proposed model, which in applying to closed-shell nuclei is arranged for practical implementations.

On the direct and semidirect neutron radiative capture by medium-heavy mass nuclei

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.