Anjali Mukherjee

7Li+12C and 7Li+13C fusion reactions at subbarrier energies

Abstract The 7Li+12C and 7Li+13C reactions have been studied at incident energies below and around the Coulomb barrier, by the measurement of cross sections for the characteristic γ-rays emitted from the residual nuclei. Statistical model calculations of the decay of the compound nucleus have been used to deduce the absolute cross sections for different channels and to obtain the total fusion cross sections. There is no evidence for fusion cross section limitations for these systems at energies near the Coulomb barrier as observed in an earlier experiment.

Fusion cross sections for 6Li+12C and 6Li+13C reactions at low energies

Abstract The partial cross sections for the 6Li+12C and 6Li+13C reactions below and above the Coulomb barrier energy have been determined from the cross sections of the characteristic γ-rays measured with HPGe detectors and using the branching factor σ γ σ ch obtained from the statistical model calculations. The fusion cross sections obtained from the sum of these partial cross sections are found to be equal to the total reaction cross sections upto an energy well above the Coulomb barrier energy and there appears to be no evidence for limitation of fusion cross sections for these systems at such energies contrary to the evaporation residue measurements. The measured cross sections are also found to agree nicely with the IWBC (Incoming Wave Boundary Condition) and one-dimensional BPM (Barrier Penetration Model) calculation.

Rotational bands in the doubly odd 138Pm

Abstract The band structures of the doubly- odd 138Pm nucleus have been investigated using the 115In(28Si, 2p3n)138Pm reaction at a beam energy of 145 MeV. The three previously known rotational bands viz., (i) the yrast one based on the πh 11 2 ⊗ νh 11 2 configuration, (ii) a ΔI = 2 band with πh 11 2 ⊗ ν[400] 1 2 + configuration at lower frequency but with a change in the neutron configuration to ν[660] 1 2 + at higher frequency, and (iii) one consisting of stretched E2 cascades at lower frequency but of dipole transitions after backbend and with suggested configuration of π[413] 5 2 + ⊗ νh 11 2 have been modified and extended to higher spins. Two new bands have been identified. Of these, one consists of only quadrupole transitions, similar to that observed in band (iii), mentioned above, while the other consists of dipole transitions. The observed level properties have been compared to theoretical calculations performed within the Particle Rotor Model (PRM) with axial core and cranked shell model. The experimental branching ratios and B (M1) , B (E2) ratios of the transitions in the yrast band are well reproduced by PRM, assuming an axial prolate core.

Oblate bands in doubly odd 134La

Abstract The band structures of the doubly odd 134La nucleus have been investigated using the 133Cs(α, 3n) 134La reaction at a beam energy of 40 MeV. Altogether six bands have been established, of which details of the yrast band were only known from earlier works. A negative parity oblate band has also been observed in this nucleus. The observed level properties of the members of the yrast band have been compared with theoretical calculations performed within the Particle Rotor Model (PRM) with axially symmetric core. The experimental branching ratios, B (M1) B (E2) values and mixing ratios of the transitions in the yrast band are well reproduced by PRM, assuming an axial oblate core. A cranked shell model calculation has been carried out for the proposed bands.

Accurate measurement of the intensity of 255.1 keV gamma ray in the decay of 113Sn(115.1d)

Abstract Using large volume HPGe detectors the intensity of the 255.1 keV γ-ray relative to the 391.7 keV γ-ray in the decay of 113 Sn (115.1 d ) has been accurately measured. This value (3.37 ± 0.05) is found to be significantly large (≈ 18%) compared to the one adopted in the literature. On the basis of the present results a revised decay scheme of 113 Sn has been constructed.

Seven-quasiparticle bands in {sup 139}Ce

The high spin states in the Ce-139 nucleus have been studied by in-beam gamma-spectroscopic techniques using the reaction Te-130(C-12,3n)Ce-139 at E-beam=65 MeV. A gamma detector array, consisting of five Compton-suppressed Clover detectors was used for coincidence measurements. 15 new levels have been proposed and 28 new gamma transitions have been assigned to Ce-139 on the basis of gamma gamma coincidence data. The level scheme of Ce-139 has been extended above the known 70 ns 19/2 isomer up to similar to 6.1 MeV in excitation energy and 35/2h in spin. The spin-parity assignments for most of the newly proposed levels have been made using the deduced Directional Correlation from Oriented states of nuclei (DCO ratio) and the Polarization Directional Correlation from Oriented states (PDCO ratio) for the de-exciting transitions. The observed level structure has been compared with a large basis shell model calculation and also with the predictions from cranked Nilsson-Strutinsky (CNS) calculations. A general consistency has been observed between these two different theoretical approaches.

Multi-quasiparticle bands in {sup 137}Ce

Excited states of {sup 137}Ce, populated in the {sup 130}Te({sup 12}C,5n) reaction at a beam energy of 65 MeV, have been investigated by {gamma}{gamma} coincidence spectroscopy using a modest Clover Ge array. Unique spin-parity assignments have been made for most of the levels at high spin and excitation energy by using DCO ratios and polarization information. The known level scheme of {sup 137}Ce has been considerably revised on the basis of the new information. A sequence of M1 transitions, developed on the 5379.1-keV (33/2)({Dirac_h}/2{pi}) level has been suggested to be a positive-parity band through unambiguous assignment of multipolarity of 1124.1- and 836.1-keV {gamma} rays. Another positive-parity bandlike structure has been seen, starting at the 2928.4-keV (19/2){sup +} level. Total Routhian surface calculations have been done to predict underlying multi-quasiparticle configurations for the observed bands.

On the EC branching to the ground state of 197Au in the decay of 197Hg (64.1 h)

Abstract From the accurate measurement of Kx-ray and γ-ray intensities in the decay of 197Hg (64.1 h) the EC branchings to different states of 197Au have been determined. The ground state branching is found to be