T. A. Ermakova

Investigation of the neutron shell structure of the even-even isotopes 40–56Ca within the dispersive optical model

Within the method of matching experimental data obtained in the neutron-stripping and neutron-pickup reactions on 40,42,44,46,48Ca isotopes, the single-particle energies and probabilities that neutron states are filled are obtained for the even-even calcium isotopes. These data are analyzed within the dispersive optical model, and good agreement between the calculated and experimental values of the energies of states is obtained. The dispersive optical potential is extrapolated to the region of the unstable 50,52,54,56Ca nuclei. The calculated single-particle energies of bound states in these isotopes are compared with the results of the calculations within the multiparticle shell model, the latter predicting a new magic number N = 34 for Z = 20 nuclei.

Investigation of special features of the neutron and proton shell structure of the isotopes 90,92,94,96Zr

The neutron and proton single-particle energies and the occupation probabilities for the valence states of the even-even isotopes 90,92,94,96Zr are determined by matching data on nucleon-stripping and nucleon-pickup reactions on the same nucleus. The data obtained in this way suggest the magicity of the number N = 56 for Z = 40. The single-particle energies of all bound neutron and proton states in the 90,92,94,96Zr nuclei are described within the experimental errors on the basis of the dispersive optical model.

Single-particle levels of nuclei in the vicinity of the doubly magic nuclei 2048Ca28 and 2856Ni28

Isotonic and isotopic dependences of single-particle energies of neutron and proton states in 20 ≤ Z ≤ 28 and 24 ≤ N ≤ 32 nuclei are investigated, these energies being determined by matching data on nucleon-stripping and nucleon-pickup reactions on the same nucleus. Regularities of the formation of the spectra of single-particle levels in Z, N = 20, 28 magic nuclei are demonstrated. A distinctive feature is found in the isotonic dependence of the energy of the 1 f5/2 neutron level, this feature being consistent with the assumption that j>-j< interaction is operative in nuclei. The single-particle energies calculated by using the potential of the dispersive optical model are found to be consistent with experimental data within their errors.

Evolution of Proton Shells in 20<Z<28 and 20<N<50 Nuclei and Dispersive Optical Model

Experimental single-particle proton energies in spherical and nearly spherical 20 ⩽ Z ⩽ 28 medium-mass nuclei and their counterparts evaluated with the aid of data formirror nuclei were analyzed on the basis of the dispersive optical model. The parameters of the dispersive optical potential were extrapolated to the region of unstable nuclei, and the values obtained in this way were then used to predict the single-particle proton energies in the 20 ⩽ N ⩽ 50 nuclei under study. The evolution of the particle-hole energy gap was traced, and features peculiar to single-particle spectra of magic and nonmagic nuclei were revealed by comparing single-particle energies with proton-separation energies.

Investigation of the shell structure of 40 ⩽ A ⩽ 132 magic and near-magic nuclei within the mean-field model involving a dispersive optical potential

Amethod for determining parameters of a dispersive optical potential is presented. This method is aimed at calculating single-particle energies of neutron and proton states of magic and near-magic nuclei. It is based on the use of global parameters of the imaginary part of the traditional-optical-model potential and experimental data on single-particle energies in the vicinity of the Fermi surface that were determined by simultaneously evaluating data on nucleon-stripping and nucleon-pickup reactions on the same nucleus. The potential of the method for describing and predicting single-particle energies of 40 ⩽ A ⩽ 132 magic and near-magic nuclei is demonstrated.

Shell structure of even-even nickel isotopes containing twenty to forty neutrons

Shell parameters of even-even nickel isotopes involving twenty to forty neutrons are analyzed, and the results of this analysis are presented. A detailed comparison of the results obtained by calculating, on the basis of the mean-field model with the Koura-Yamada potential and the dispersive optical potential, single-particle energies of proton and neutron subshells with experimental data on the isotopes 56,58,60,62,64,68Ni and with evaluated data on the neutron-deficient isotopes 48,50,52,54Ni is performed.

Energies of the single-particle proton 1f and 2p states in the 58,60,62,64Ni isotopes

Single-particle energies corresponding to the maximum value of the spectroscopic factor were obtained for the proton states near the Fermi energy in the 58,60,62,64Ni nuclei by the joint evaluation of the data on the stripping and pickup reactions on the same nucleus. These results are compared with the center-of-gravity energies of the single-particle state fragment distributions obtained by the same method and with the single-particle energies calculated with the potential of X. Koura and M. Yamada and with the dispersive optical model potential. The single-particle state fragmentation effect is discussed.

Dispersive optical potential from an analysis of neutron single-particle energies in the Ti, Cr, and Fe isotopes featuring 20 to 50 neutrons

Neutron single-particle energies in unstable Ti, Cr, and Fe isotopes containing 20 to 26 neutrons were evaluated on the basis of experimental proton energies in the mirror-symmetric nuclei. The neutron single-particle energies in the 20 ⩽ N ⩽ 50 Ti, Cr, and Fe isotopes were calculated on the basis of the mean-field model with a dispersive optical potential, and the results were compared with available experimental data and with the results of estimations and calculations based on the relativistic mean-field model and on the multiparticle shell model with the GXPF1 interaction.

Analysis of single-particle energies of the neutron states in the 64,66,68,70Zn isotopes within a mean field model with dispersive optical potential

The dynamics of the shell parameters of 64, 66, 68, 70Zn nuclei close to the Fermi energy, obtained by the joint evaluation of data from the stripping and pick-up reaction of a nucleon on one and the same nucleus, demonstrates how the difference between the neutron single-particle spectra of the levels of 70Zn and 68Ni nuclei with the number N = 40 arises. The experimental data are analyzed within a mean field model with dispersive optical potential. The calculation results describe very well the dimunution of the energy gap between the 1g9/2 and 2p1/2 levels in Zn isotopes, in comparison with Ni isotopes.

Analysis of proton single-particle properties of zinc and germanium isotopes

Experimental proton single-particle energies in the vicinity of the Fermi energy for stable zinc and germanium isotopes are analyzed on the basis the dispersive optical model. The values found for the parameters of the dispersive optical potential are corrected with the aim of matching the total number of protons that is calculated with the aid of the function of Bardeen-Cooper-Schrieffer theory for the occupation probability for single-particle orbits with the charge number Z of the nucleus. The parameters of the dispersive optical potential are extrapolated on the basis of physically motivated arguments to the region of unstable isotopes in which the number N ranges between 34 and 50, and single-particle spectra are predicted by means of calculations with these parameters.