• Tumpa Bhattacharjee

      Articles written in Pramana – Journal of Physics

    • High spin spectroscopy of 139Pr

      S Chanda Sarmishtha Bhattacharyya Tumpa Bhattacharjee SS Ghugre Swapan Kumar Basu S Muralithar RP Singh B Mukherjee RK Bhowmik SN Ray

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      The high spin states in N=80 139Pr have been investigated by in-beam γ-spectroscopic techniques following the reaction 130Te (14N, 5n) reaction at E=75 MeV, using a gamma detector array, consisting of seven 23% compton-suppressed high purity germanium detectors and a multiplicity ball of fourteen bismuth germanate elements. Based on γ-γ coincidence data, the level scheme of 139Pr has been considerably extended up to 7.2 MeV excitation. Tentative spin-parity assignments are done for the newly proposed levels on the basis of the DCO ratios corresponding to strong gates and the available information from the earlier light ion experiments.

    • Structure of $A \sim130$ nuclei in La–Ce region

      Tumpa Bhattacharjee

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      The variety of shapes and structures, observed in light rare earth $A \sim 130$ nuclei, have been discussed in view of different angular momentum coupling schemes and their interplay that comes into effect at high spin. The $N = 79$ and 80 isotopes in La–Ce region, produced via fusion evaporation reaction, have been studied using the Indian National Gamma Array (INGA) consisting of 18 clover HPGe detectors. Two nearly degenerate $\Delta I = 1$ bands have been observed at high spin of 137Ce and a triaxial deformation of $\gamma = \pm 30^{\circ}$ has been assigned to the bands, from the total Routhian surface (TRS) calculations. The high-spin candidates of the yrast band of 138Ce show signature splitting both in energy and $B(M1)/B(E2)$ values. The bandcrossing due to the alignment of a pair of $h_{11}/2$ proton particles has been conjectured at $\hbar ω \sim 0.3$ MeV, from the single-particle Routhians obtained from TRS calculations. Lifetime measurements by Doppler shift attenuation method (DSAM) has been carried out and from the estimated reduced transition probability $B(M 1)$, the $\Delta I = 1$ band in 138Ce has been characterized as a magnetic rotation (MR) band. The rise in the values of $B(M1)$, for the higher spin candidates of the band, has been conjectured as the reopening of a different shear at the top of the Band B1. The characteristic of the MR bands in $A \sim 130$ region has been discussed in the light of a phenomenological calculation and compared to the MR bands in other mass regions.

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