I. Mehrotra

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.

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.

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.

Parity Inversion and Different Properties of 4Be11 Halo Nuclei

The recent developments of radioactive nuclear beams has opened up the possibility of exploring a wide variety of nuclei far from the valley of beta‐stability. Of late several theoretical studies have come up in the past for describing nuclei in these exotic region. Extension of traditional shell model techniques to explain the exotic feature in the structure of these nuclei such as, formation of neutron halo large r.m.s radii, soft dipole resonances etc have confirmed the necessity to modify the single particle shell model potential when dealing with nuclei far from stability. The ground state nuclear structure properties of 4Be11 have been calculated in the framework of shell model using analytically soluble mean field potential given by Ginocchio. The potential is highly versatile in nature and depends on four parameters, which define its depth, range and shape. Potential parameters, which generate highly diffilse shape, account for the small binding and halo structure of the valence neutron in 4Be11. ...The recent developments of radioactive nuclear beams has opened up the possibility of exploring a wide variety of nuclei far from the valley of beta-stability. Of late several theoretical studies have come up in the past for describing nuclei in these exotic region. Extension of traditional shell model techniques to explain the exotic feature in the structure of these nuclei such as, formation of neutron halo large r.m.s radii, soft dipole resonances etc have confirmed the necessity to modify the single particle shell model potential when dealing with nuclei far from stability. The ground state nuclear structure properties of 4Be11 have been calculated in the framework of shell model using analytically soluble mean field potential given by Ginocchio. The potential is highly versatile in nature and depends on four parameters, which define its depth, range and shape. Potential parameters, which generate highly diffuse shape, account for the small binding and halo structure of the valence neutron in 4Be11. The problem of ground state parity inversion is also addressed.