Z. Naik

Small quadrupole deformation for the dipole bands in 112 In

High spin states in 112 In were investigated using the 100 Mo( 16 O ,p 3n) reaction at 80 MeV. The excited level has been observed up to 5.6 MeV excitation energy and spin ∼20¯ h with the level scheme showing three dipole bands. Polarization and lifetime measurements were carried out for the dipole bands. Tilted axis cranking model calculations were performed for different quasiparticle configurations of this doubly odd nucleus. Comparison of the calculations of the model with the B(M1) transition strengths of the positive- and negative-parity bands firmly established their configurations.

Shape coexistence and high spin states in {sup 52}Cr

High spin states in {sup 52}Cr have been populated by means of the reaction {sup 27}Al({sup 28}Si,3p){sup 52}Cr at a beam energy of 70 MeV and studied with an array, consisting of eight Compton-suppressed clover germanium detectors. Eleven new {gamma} rays have been assigned to {sup 52}Cr and placed in the level scheme. The level structure of {sup 52}Cr has been extended up to E{sub x}{approx_equal}10 MeV. Spins and parities have been assigned to many of the levels on the basis of directional correlations and linear polarization measurements. The band structures are discussed in the framework of cranked Woods-Saxon and deformed Hartree-Fock (HF) models. Both the oblate and prolate orbits are considered for J projection in the HF model. The K=0{sup +} band is properly understood if we consider the J projection from both prolate and oblate orbits and collectivity shown by the K=4{sup +} band to be accounted for by taking the J projection from prolate HF configurations. Thus there is prolate and oblate shape coexistence in {sup 52}Cr.

Structure of Dipole Bands in 112In: Through Lifetime Measurement

High-spin states of the 112In nucleus have been populated via 100Mo(16O, p3n) reaction at 80 MeV beam energy. Lifetimes of excited states of dipole bands have been measured using Doppler-shift attenuation method. The B(M1) transition rates deduced from the measured lifetimes show a rapid decrease with increasing angular momentum. The decrease in B(M1) values are well accounted by the prediction of tilted axis cranking calculations. These measurements confirm the presence of shears mechanism in this nuclei.

Shape evolution at high spin states in Kr and Br isotopes

The high spin states in A = 75, Kr and Br isotopes have been populated via fusion-evaporation reaction at an incident beam energy of 90 MeV. The de-exciting γ-rays were detected utilizing the Indian National Gamma Array (INGA). Lifetime of these excited high spin states were determined by Doppler-shift attenuation method. Experimental results obtained from lifetime measurement are interpreted in the frame work of projected shell-model to get better insight into the evolution of collectivity. Comparison of the calculations of the model with transitional quadrupole moments Qt of the positive and negative parity bands firmly established their configurations.

Polarization measurements and high spin structure in 131Ba

The high spin states of 131Ba have been populated in the fusion evaporation reaction 122Sn(13C,4n)131Ba at Ebeam = 65MeV. The γ transitions belonging to various band structures were detected using an array of fifteen Clover Germanium detectors. Some of new transitions have been placed in high spin states. Spin and parity for a band has been calculated for first time in 131Ba. The said band is interpreted in term of multi-quasiparticle configurations, based on Total Rothian Surfaces (TRS) calculations.

Excited states in {sup 99}Pd

Excited states in the {sup 99}Pd nucleus populated in the {sup 75}As({sup 28}Si, p3n) fusion-evaporation reaction at E{sub lab}=120 MeV have been investigated through in-beam {gamma}-ray spectroscopic techniques using an array of Compton-suppressed clover detectors. The level scheme is established up to excitation energy {approx}11.5 MeV and spin {approx}25({h_bar}/2{pi}) with the addition of about 60 new transitions. The level structures observed in {sup 99}Pd have been interpreted in the framework of a microscopic theory based on the deformed Hartree-Fock and angular momentum projection techniques. Band structures at lower spins are based on the low-{Omega} {nu}g{sub 7/2} and {nu}d{sub 5/2} orbitals, and those at higher spins are reproduced for the {pi}(g{sub 9/2}){sup 5} x {pi}(g{sub 7/2}) x {nu}(g{sub 7/2}){sup 2} x {nu}(h{sub 11/2}){sup 2} x {nu}(g{sub 9/2}){sup -1} and {pi}(g{sub 9/2}){sup 6} x {nu}(g{sub 9/2}){sup 10} x {nu}(g{sub 7/2}){sup 2} x {nu}(h{sub 11/2}) configurations. The octupole correlations in {sup 99}Pd have been inferred from new interband E1 transitions linking the {Delta}I=1 states of the bands based on the {nu}h{sub 11/2} and {nu}d{sub 5/2} orbitals ({Delta}l=3, {Delta}j=3, and {Delta}{pi}=-1) with the deduced B(E1) values {approx}10{sup -6} W.u.

Band structure and shape coexistence in {sub 56}{sup 135}Ba{sub 79}

Excited states of {sub 56}{sup 135}Ba{sub 79} at high spins are studied using the reaction {sup 130}Te({sup 9}Be,4n){sub 56}{sup 135}Ba{sub 79} at 42.5-MeV beam energy. The earlier known level scheme is extended up to 6.4-MeV excitation energy and (37/2)(Planck constant/2pi) spin with the addition of several transitions. We have performed polarization asymmetry measurements for some of the strong transitions by using a Clover detector to assign the parity. A comparison of experimental data with the results of tilted axis cranking calculations based on various configurations indicates the coexistence of multiple minima in the triaxial deformation (gamma), whereas axial symmetric deformation (epsilon{sub 2}) remains constant around 0.09.

Band structures in {sup 129}Cs

The {sup 122}Sn({sup 11}B,4n) fusion-evaporation reaction at E{sub lab}=60 MeV was used to populate excited states in {sup 129}Cs, and the deexcitations were investigated using in-beam {gamma}-ray spectroscopic techniques. The level scheme of {sup 129}Cs is established up to {approx}8 MeV excitation energy and 47/2 h spin. The observed band structures are interpreted for their configurations in the framework of cranking model calculations and systematic of the neighboring {sub 55}Cs isotopes. A negative-parity {delta}I=1 coupled band has been assigned the {pi}h{sub 11/2} x {nu}(h{sub 11/2}){sup 2} configuration as solution of the tilted-axis cranking, which coexists with the {pi}h{sub 11/2} yrast band resulting from the principal-axis cranking. A new band has been identified as a {gamma}-vibrational band built on the {pi}h{sub 11/2} orbital. A pair of strongly coupled positive-parity bands exhibiting similar features have been assigned different unpaired three-quasiparticle configurations involving the {pi}h{sub 11/2} x {nu}h{sub 11/2} component. The previously identified unfavored signature partners of the {pi}d{sub 5/2} and {pi}g{sub 7/2} bands are reassigned as {gamma} vibrations of the core coupled to the {pi}g{sub 7/2} single-particle configuration, and the favored signature of the {pi}d{sub 5/2} band, respectively.

Shape evolution of the highly deformed {sup 75}Kr nucleus examined with the Doppler-shift attenuation method

High-spin states of the {sup 75}Kr nucleus have been populated via the {sup 50}Cr({sup 28}Si,2pn){sup 75}Kr reaction at an incident beam energy of 90 MeV. Lifetimes of nine states up to spin I=33/2 for the positive-parity band and seven states up to I=27/2 for the negative-parity band have been measured using the Doppler-shift attenuation method. The deduced transition quadrupole moments Q{sub t} of these bands have been compared to the projected shell-model calculations to gain insight into the evolution of collectivity for the two experimentally studied bands in {sup 75}Kr.

Structure of dipole bands in {sup 106}In

High spin states in neutron-deficient {sup 106}In were investigated using {sup 78}Se({sup 32}S,p3n) reaction at 125 MeV. The level scheme is extended up to 7 MeV of excitation energy for the negative parity states constituting four dipole bands, and the positive parity states which mainly exhibit single-particle excitations are extended up to 5 MeV. Projected deformed Hartree-Fock calculations were carried out to understand the configurations of different bands in this nucleus.