Semimicroscopic Description Research Articles

Properties of charge-exchange giant spin-dipole resonances in medium-heavy closed-shell parent nuclei: A semimicroscopic description

Properties of charge-exchange giant spin-dipole resonances in medium-heavy closed-shell parent nuclei: A semimicroscopic description

Semimicroscopic description of isoscalar giant multipole resonances in medium-mass closed-shell nuclei

Semimicroscopic description of isoscalar giant multipole resonances in medium-mass closed-shell nuclei

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.

Quantum wires, Chern-Simons theory, and dualities in the quantum Hall system

Over the years, many theoretical frameworks have been developed to understand the remarkable physics of the quantum Hall system. In this work we discuss the interplay among quantum wires, Chern-Simons theory, bosonization, and particle-vortex duality, which enable a unified approach for the Laughlin states of the fractional quantum Hall system. Starting from the so-called quantum wires system, which is a semi-microscopic description in terms of 1+1 dimensional theories, we discuss the emergence of 2+1 dimensional low-energy effective field theories by using different maps connecting the microscopic degrees of freedom with the macroscopic ones. We show the origin of these maps by embedding the bosonized version of the original quantum wires model in a gauge invariant theory and using particle vortex-duality.

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.

Semi-microscopic description of the proton-and neutron-induced backbending phenomena in some deformed even-even rare earth nuclei

A semi-microscopic model to study the double backbending phenomenon in some deformed even-even nuclei from the rare earth region is proposed. The backbending phenomena are described by mixing four rotational bands, defined by a set of angular momentum projected states with a specific single-particle factor, and a model Hamiltonian describing a set of paired particles moving in a deformed mean field and interacting with a phenomenological deformed core. Due to the specific construction, the wave function acquires a complex structure which allows a quantitative description of the yrast states in the region of the two backbendings.

Erratum: Semimicroscopic description of backbending phenomena in some deformed even-even nuclei [Phys. Rev. C84, 044323 (2011)

Received 18 December 2012DOI:https://doi.org/10.1103/PhysRevC.87.029901©2013 American Physical Society

Semi-microscopic description of the double backbending in some deformed even–even rare earth nuclei

A semi-microscopic model to study the neutron- and proton-induced backbending phenomena in some deformed even–even nuclei from the rare earth region is proposed. The space of particle–core states is defined by the angular momentum projection of a quadrupole deformed product state. The backbending phenomena are described by mixing four rotational bands, defined by a set of angular momentum projected states, and a model Hamiltonian describing a set of paired particles moving in a deformed mean field and interacting with a phenomenological deformed core. The ground band corresponds to the configuration where all particles are paired, while the other rotational bands are built on one neutron or/and one proton broken pair. Four rare earth even–even nuclei which present the second anomaly in the observed moments of inertia are successfully treated within the proposed model.

Semimicroscopic description of basic modes of relaxation of the Gamow-Teller resonance

Semimicroscopic approach based on the continuum version of the random-phase approximation and on a phenomenological method for taking into account the fragmentation effect is used to describe quantitatively basic relaxation parameters of the Gamow-Teller resonance in magic and nearmagic nuclei. For the 208Bi nucleus, the results obtained by calculating the resonance parameters in question are compared with respective experimental data.

Simplest photonuclear reactions accompanied by the excitation of isovector giant dipole and quadrupole resonances: Semimicroscopic description

A semimicroscopic approach based on the continuum version of the random-phase approximation (CRPA) and on a semiphenomenological inclusion of the fragmentation effect is applied to describing cross sections for photoabsorption and direct plus semidirect and inverse reactions accompanied by the excitation of isovector giant dipole and quadrupole resonances. In addition to the spinless part of the Landau-Migdal interaction and a partly self-consistent phenomenological mean field of the nucleus, that version of the approach which is used here takes into account isovector separable velocity-dependent forces, as well as the effect of the fragmentation shift of the giant-resonance energy. The results obtained by calculating various features of the aforementioned cross sections for a number of magic and semimagic medium-mass nuclei are compared with respective experimental data.

Semimicroscopic description of backbending phenomena in some deformed even-even nuclei

The mechanism of backbending is semi-phenomenologically investigated based on the hybridization of two rotational bands. These bands are defined by treating a model Hamiltonian describing two interacting subsystems: a set of particles moving in a deformed mean field and interacting among themselves through an effective pairing force and a phenomenological deformed core whose intrinsic ground state is an axially symmetric coherent boson state. The two components interact with each other by a quadrupole-quadrupole and a spin-spin interaction. The total Hamiltonian is considered in the space of states with good angular momentum, projected from a quadrupole deformed product function. The single-particle factor function defines the nature of the rotational bands, one corresponding to the ground band in which all particles are paired and another one built upon a $i_{13/2}$ neutron broken pair. The formalism is applied to six deformed even-even nuclei, known as being good backbenders. Agreement between theory and experiment is fairly good.

Relaxation of giant resonances: Semimicroscopic description (Methods, Results, and Prospects)

An account of a semimicroscopic approach to globally describing dominant relaxation modes for giant resonances in spherical nuclei is given. This approach is based on the continuum version of the random-phase approximation and on a phenomenological description of the fragmentation effect. The fragmentation effect in question is taken into account in the “pole” approximation in terms of the excitationenergy-dependent imaginary part of the single-particle effective optical potential directly in the equations of the approximation in question. In the practical implementation of the above approach, use is made of the Landau-Migdal interaction in the particle-hole channel and a phenomenological mean field of the nucleus being considered, these two being related by a partial-consistency condition. The results obtained within this approach by calculating integrated and differential features for a number of giant resonances over a broad range of excitation energies are used to perform a comparison with available experimental data and to predict the results of possible experiments. A particle-hole optical model that serves both as a substantiation for the existing version of the semimicroscopic approach and as a basic element for describing excitations of the particle-hole type at an arbitrary (albeit rather high) energy is formulated.

Semimicroscopic description of the spreading width of isobaric analog resonances in spherical nuclei

A method for semimicroscopic description of the spreading width of isobaric analog resonances (IARs) is applied to the IAR built on the 91Zr, 208,209Pb ground state. This width is expressed in terms of the mean Coulomb field and the imaginary part of the effective optical potential used to describe the total width of the IAR overtone—isovector giant monopole resonance.

Semimicroscopic description of charge-exchange giant spin-monopole resonances

The quantitative analysis of the main properties of charge-exchange giant spin-monopole resonances is performed for closed-shell parent nuclei within the semimicroscopic approach based on the continuum version of the random phase approximation and phenomenological treatment of the spreading effect. For the first time the description of direct neutron decay of the spin-monopole resonances in the β+-channel is given together with taking into account the resonance energy shift due to the spreading effect. The results of the joint analysis of the main properties of the above-mentioned giant resonances are given for the parent nuclei 48Ca and 208Pb.

Semimicroscopic description of the giant dipole resonance

A simple semimicroscopic model providing the possibility of taking into account the influence of deformation, configuration, and isospin effects on the structure of giant dipole resonance is formulated. This model is applied for the description of global specific features of photoabsorption cross sections for spherical, deformed, and transition nuclei in the mass region 10 ≲ A ≲ 240.

On a semimicroscopic description of extremely simple photonuclear reactions involving the excitation of a giant dipole resonance

A quantitative interpretation of basic properties of a giant dipole resonance is proposed within a semimicroscopic approach relying on the random-phase approximation that takes exactly into account a single-particle continuum and on a phenomenological description of the fragmentation effect. For some magic and semimagic nuclei, the calculated photoabsorption cross sections and cross sections for partial photoneutron “direct + semidirect” reactions in the vicinity of the above resonance are compared with their experimental counterparts.

Semimicroscopic description of the gross structure of giant dipole resonances in carbon, nitrogen, and oxygen isotopes

A version of a semimicroscopic description of dipole nuclear vibrations is formulated in such a way that the deformation, the configuration, and the isospin splitting of a giant dipole resonance are taken simultaneously into account. This model is used to describe the main structural features of the cross sections for photoabsorption on 12,13,14C, 14,15N, and 16,17,18O nuclei.

Semimicroscopic description of basic properties of isoscalar monopole and dipole excitations in medium-mass spherical nuclei

A description of basic properties (strength function, transition density, probabilities of direct nucleonic decays) of isoscalar giant monopole (including an overtone) and dipole resonances in medium-mass spherical nuclei is proposed within a semimicroscopic approach. The approach relies on employing the random-phase approximation and involves taking exactly into account a single-particle continuum and some conditions of partial self-consistency and phenomenologically describing the coupling of states of the particle-hole type to multiquasiparticle configurations. The results of the calculations that were performed for 90Zr, 116,124Sn, 144Sm, and 208Pb nuclei are compared with available experimental data.

Semimicroscopic description of the gross structure of a giant dipole resonance in light nonmagic nuclei

A simple model is formulated that makes it possible to describe the configuration and deformation splittings of a giant dipole resonance in light nonmagic nuclei. The gross structure of the cross sections for photoabsorption on 12C, 24Mg, and 28Si nuclei is described on the basis of this model.