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The low-lying energy levels, B(E2) transition probabilities and g-factors of even–even medium-mass tellurium isotopes have been studied by employing the projected shell model (PSM) approach. The oblate ground state deformations are taken in this study that were predicted in previous relativistic Hartree Bogoliubov mean field study. The low-lying yrast and yrare states are reproduced well in these calculations. The energy and configuration of yre states are also predicted. The experimental B(E2) values and their systematics with neutron number are reproduced well in the medium-mass Te isotopes. The experimental data are available for g -factors of 2 + states of 1 2 0 , 1 2 2 Te isotopes which is in line with these calculations. The enhancement of g-factors at spin I = 6 + in all the Te isotopes considered may be attributable to the alignment of protons in (π g 7 / 2) 2 subshell. Furthermore, the reduction of g-factors at spin I = 1 0 + in 1 1 4 − 1 1 8 Te and I = 8 + in 1 2 0 , 1 2 2 Te may be attributable to the alignment of neutrons in the (ν h 1 1 / 2) 2 subshell. The 8 + states of 1 1 4 − 1 1 8 Te are envisaged to be of (π g 7 / 2) 2 nature and in 1 2 0 , 1 2 2 Te these states are found to be of (ν h 1 1 / 2) 2 nature. [ABSTRACT FROM AUTHOR]

Lifetime measurements of excited states in doubly-magic 56Ni have been performed exploiting the Doppler-shift attenuation method in order to determine reduced transition probabilities. For the 41+ and 61+ states, the deduced B(E2) values are compared with results from shell-model calculations employing the GXPF1A and the modern PFSDG-U interactions. In addition, valence ab-initio calculations were performed using a novel realistic Hamiltonian derived from chiral perturbation theory including three-body potential contributions and are confronted with the experimental findings. The new results show maximum E2 strength in comparison with known values along the N=28 chain of isotones. The results corroborate the high collectivity for the double shell closure at N=Z=28 which was anticipated from the large B(E2;21+→0g.s.+) value despite the considerable increase of its excitation energy as compared to neighboring semi-magic nuclei. Based on similarities in the shell structures of the self-conjugate doubly-magic nuclei 56Ni and 100Sn, the new values could be an indication for an expected comparable collective behavior of the 61+ state in 100Sn.

Lifetimes of the 21+ states in 44Ti, 48,50Cr, and 52Fe were determined with high accuracy exploiting the recoil distance Doppler-shift method. The reduced E2 transition strengths of 44Ti and 52Fe differ considerably from previously known values. A systematic increase in collectivity is found for the N=Z nuclei compared to neighboring isotopes. The B(E2) values along the Ti, Cr, and Fe isotopic chains are compared to shell-model calculations employing established interactions for the 0f1p shell, as well as a novel effective shell-model Hamiltonian starting from a realistic nucleon–nucleon potential. The theoretical approaches underestimate the B(E2) values for the lower-mass Ti isotopes. Strong indication is found for particle-hole cross-shell configurations, recently corroborated by similar results for the neighboring isotone 42Ca.

A description of the even-even Hf isotopes for A = 172 - 176 is carried out in the framework of the interacting boson model (IBM-1). The energy levels, B(E2) transition probabilities, electric quadrupole moment QL, and potential energy surface of those nuclei have been calculated. The calculated results are compared with the most recent experimental data. A good agreement for low lying energy states is obtained between experimental results and theoretical calculations. The contour plots of the potential energy surfaces show that the interested nuclei have rotational characters. [ABSTRACT FROM AUTHOR]

Interacting Boson Model (IBM -1) has been used to study the energy levels and transition rates in Ba-Dy () isotones. A simplified Hamiltonian is used which is written in the creation and annihilation form and for each nucleus, by fitting the selected experimental energy levels and transition rates with the calculated ones to get the best model parameters. Using the (IBM) Hamiltonian with an intrinsic state formalism, the potential energy surfaces (PES) for even-even Ba-Dy nuclei have been obtained and the contour plot of PES show that the shape phase transitions from spherical to deformed shape has been determined for the , while Ce, Nd, Sm, Gd and Dy nuclei are deformed and have rotational-like characters. The behavior of energy and ratios in the ground state band are examined. [ABSTRACT FROM AUTHOR]

Two new numbers, ν and ζ, inspired by particle-hole symmetry are introduced. These numbers have extreme values at a closed shell and vanish mid-shell. A combination of even powers of these numbers has been used to model experimentally measured quantities such as R4/2=E(4+1)/E(2+1) and the “microscopic” contribution to binding energies. A binding energy fit consisting of a total of six fit coefficients, including one new shell term, reproduces the experimental binding energies of 2353 nuclei with an r.m.s. standard deviation of 1.55 MeV. The difference between the experimental and fit values of observables, specifically the R4/2, provides an indication of where shell closure features are less pronounced and where sub-shells closures occur. [ABSTRACT FROM AUTHOR]

We describe α -transitions to low-lying states in even–even nuclei with Z > 50 , N > 82 using the Coherent State Model (CSM). We reproduce the energy levels and electromagnetic transition rates between the states of the ground band employing two parameters, namely the deformation parameter and the strength of the harmonic CSM Hamiltonian. The B(E2) values are described in terms of an effective charge which depends linearly on the deformation parameter. The treatment of the α -emission process is based on an α –daughter interaction containing a monopole component, calculated through a double folding procedure with a M3Y interaction plus a repulsive core simulating the Pauli principle, and a quadrupole–quadrupole (QQ) interaction. The decaying states are identified with the lowest narrow outgoing resonances obtained through the coupled channels method. The α -branching ratios to 2 + states are reproduced by means of the QQ strength. This interaction strength can be fitted with a linear dependence on the deformation parameter, as predicted by the CSM. The theoretical intensities to 4 + and 6 + states are in reasonable agreement with available experimental data. Predictions are made for spherical, transitional and well deformed even–even α -emitters. [ABSTRACT FROM AUTHOR]

Lifetime measurements of excited states in doubly-magic 56Ni have been performed exploiting the Doppler-shift attenuation method in order to determine reduced transition probabilities. For the 4 1 + and 6 1 + states, the deduced B (E2) values are compared with results from shell-model calculations employing the GXPF1A and the modern PFSDG-U interactions. In addition, valence ab-initio calculations were performed using a novel realistic Hamiltonian derived from chiral perturbation theory including three-body potential contributions and are confronted with the experimental findings. The new results show maximum E2 strength in comparison with known values along the N = 28 chain of isotones. The results corroborate the high collectivity for the double shell closure at N = Z = 28 which was anticipated from the large B (E2 ; 2 1 + → 0 g. s. +) value despite the considerable increase of its excitation energy as compared to neighboring semi-magic nuclei. Based on similarities in the shell structures of the self-conjugate doubly-magic nuclei 56Ni and 100Sn, the new values could be an indication for an expected comparable collective behavior of the 6 1 + state in 100Sn. [ABSTRACT FROM AUTHOR]