S. K. Khosa

Projected shell model study of the yrast bands of neutron-deficient 126–130Ce isotopes

The yrast bands of neutron-deficient 126–130Ce nuclei are studied by using the projected shell model approach. Energy levels, moments of inertia and B(E2) transition probabilities are calculated and compared with the available experimental data. The first and second backbending in 128,130Ce are investigated. The question as to why the backbending becomes sharp as the neutron number increases in cerium isotopes is addressed. It turns out that the first backbending is caused by a proton pair and the second backbending in 128,130Ce is due to a simultaneous proton and neutron pair breaking.

Microscopic study of deformation systematics and low-lying yrast spectra in even-even ruthenium isotopes

Abstract The yrast spectra with J max π = 10 + and the observed systematics of the low-lying states in 94–112 Ru nuclei are examined by carrying out Hartree-Fock-Bogoliubov calculations employing a pairing-plus-quadrupole-quadrupole effective interaction operating in a reasonably large valence space outside the 76 Sr core. Our calculations reveal that the systematics of the low-lying yrast states in 94–112 Ru are intricately linked with the deformation-producing tendency of np interaction when operating between spin-orbit partner (SOP) orbits. Our results indicate that such systematics depend crucially on the simultaneous increase of the relative occupation probabilities of ( d 5 2 ) π −( d 3 2 ) v and ( g 9 2 ) π −( g 7 2 ) v SO

E2 transition and QJ+ systematics of even-mass ruthenium nuclei

The yrast spectra with Jmaxpi = 10+, B(E2) transition probabilities and QJ+ values are calculated for even-even ruthenium isotopes by carrying out variation after projection (VAP) calculations in conjunction with the Hartree-Fock-Bogoliubov (HFB) ansatz employing a pairing-plus-quadrupole-quadrupole effective interaction operating in a reasonably large valence space outside the 76Sr core. Our calculations describe the shape changes as a function of mass number for ruthenium isotopes and also reveal that both the HFB technique as well as the quadrupole-plus-pairing-quadrupole model of the two-body interaction are fairly reliable in this mass region.

A MICROSCOPIC PERSPECTIVE ON STRUCTURE OF YRAST BANDS IN 100-112Ru ISOTOPES

The projected shell model (PSM) study of 100-112Ru nuclei is carried out. The reliability of the ground state wave functions is checked by reproducing yrast spectra and electromagnetic properties. The results of calculations indicate that the observed deformation systematics in 100-112Ru isotopes depends on the increase of occupation probability of (1h11/2)ν orbit and the deformation producing tendency of n–p interaction operating between spin orbit partner (SOP) orbits (d5/2)π-(d3/2)ν and (g9/2)π-(g7/2)ν. Besides this, the results on band diagrams show that the yrast spectra in Ru isotopes do not arise from a single intrinsic state only but also from multi-quasiparticle states.

A study of neutron-deficient 122–128Ba isotopes in the projected shell model framework

The projected shell model calculational framework is employed here for studying the nuclear structure determining properties such as high-spin yrast spectra, B(E2) transition probabilities and g-factors for neutron-deficient 122–128Ba isotopes. It turns out that a dip in B(E2) values and a peak in g-factors are correlated with crossing of the ground state band by multi-quasiparticle bands and alignment of a pair of protons in 1h11/2 subshell.

Optical and electrical characteristics of pure and doped potassium hydrogen tartrate single crystals

The optical and electrical characteristics of pure, sodium- and lithium-doped potassium hydrogen tartrate crystals grown by the gel technique are reported. An optical absorption study conducted in the UV–Vis range of 200–800 nm reveals the transparency of these crystals in the entire visible range but not in the ultraviolet range. The optical band gap of pure potassium hydrogen tartrate crystals is found to be dependent on doping by Na or Li ions. The non-linear optical behaviour of these crystals is reported and explained. The electrical properties of pure and doped potassium hydrogen tartrate crystals are studied by measuring electrical resistivity from 80 to 300 K. It is shown that while pure potassium hydrogen tartrate crystal is an insulator at room temperature (300 K), doping by Na or Li ions makes it a semiconductor. The results have been explained in terms of the variable range hopping model.

THEORETICAL INVESTIGATION OF POSITIVE PARITY BAND STRUCTURE OF Y AND Nb ISOTOPES

The positive parity band structure of odd mass neutron-rich 97–103Y and 99–105Nb nuclei has been studied using microscopic technique known as the projected shell model (PSM) with the deformed single-particle states generated by the standard Nilsson potential. The nuclear structure properties like yrast spectra, energy splitting, moment of inertia, rotational frequencies and reduced transition probabilities B(M1) and B(E2) have been calculated and their comparison with the available experimental data has been made. A shape evolution has also been predicted in these isotopes as one moves from 97Y to 99Y and 99Nb to 101Nb. The PSM calculations also demonstrate the multi-quasiparticle structure in these nuclei.

Study of 242−248Cm isotopes in the projected shell model framework

The projected shell model framework is employed to study the band spectra in 242−248Cm isotopes. The present calculations reproduce the available experimental data on the yrast bands. Besides this, B(E2) transition probabilities of even–even Cm isotopes have also been calculated. The low spin states of yrast band are seen to arise purely from zero-quasi-particle (o-qp) intrinsic states whereas the high spin states have multi-quasi-particle structure. For the odd-neutron (odd-N) isotopes, the calculated results qualitatively reproduce the available data on ground and lowest excited state bands for 243,245Cm. However, for 247Cm the negative-parity ground state band is in reasonable agreement with the experimental data.

Theoretical study of neutron-rich 107,109,111,113Rh isotopes

A theoretical study of the structure of some odd mass Rh nuclei in the A ~ 100 mass region is carried out by using the angular momentum projection technique implemented in the projected shell model (PSM). The influence of the high-j orbitals (h11/2 for neutrons and g9/2 for protons) on the structure of 107–113Rh isotopes is investigated in the present case by assuming an axial symmetry in the deformed basis. For these isotopes, the structure of multi-quasi-particle qp bands is studied along the yrast line in detail. Further, the phenomenon of back-bending is also studied theoretically and is found to be in agreement with the experimental data. The reduced transition probabilities, i.e., B(E2) and B(M1) for the yrast band are also obtained from the PSM wave functions for the first time, thereby providing an opportunity for the experimentalists to work for this data.

MICROSCOPIC STUDY OF NEGATIVE PARITY YRAST STATES IN NEUTRON-DEFICIENT 119–127Ba ISOTOPES

The negative parity yrast bands of neutron-deficient 119–127Ba nuclei are studied by using the Projected Shell Model approach. Energy levels, transition energies and B(M1)/B(E2) ratios are calculated and compared with the available experimental data. The calculations reproduce the band head spins of negative parity yrast bands and indicate the multi-quasiparticle structure for these bands.