Browsing by Author "A.K. Mondal"

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Alignment effects in the medium-spin level structure of Se 78
(American Physical Society, 2022) K. Mandal; A. Chakraborty; A.K. Mondal; U.S. Ghosh; Aniruddha Dey; Saumyajit Biswas; B. Mukherjee; S. Rai; S. Chatterjee; S.K. Das; S. Samanta; R. Raut; S.S. Ghugre; S. Bhattacharyya; S. Nandi; S. Bhattacharya; G. Mukherjee; S. Ali; A. Goswami; S. Mukhopadhyay; Krishichayan; R. Banik; R. Chakrabarti; V. Kumar; A. Kumar
The excited states of Se78 were populated using the Ge76(α,2n) fusion evaporation reaction. The deexcited gamma rays were detected using the Indian National Gamma Array (INGA) spectrometer comprising clover and low-energy photon spectrometer (LEPS) detectors. The ground state band of Se78 has been extended up to Ex = 8.5 MeV and J = 16â ; this excitation regime is very close to the π(1g9/22) crossing frequency. Several newly observed in-band and intraband transitions belonging to the other bands of Se78 have also been placed in the level scheme based on their coincidence relationships. From the newly identified E1 transitions, an enhancement in the B(E1)/B(E2) values with spin has been observed which indicates the onset of octupole correlations in the band structure built on the 3-, 2508-keV state. Persistence of triaxial shape up to the highest observed spin of the ground state band has been observed and the feature of successive 1g9/22 quasiparticle alignments due to protons and neutrons has been unveiled. The consequences arising due to the occurrence of the neutron 1g9/2 quasiparticle alignments in the other observed correlated band structures are also presented. The results are interpreted in terms of total Routhian surface (TRS) calculations and the level structure systematic of the neighboring nuclei. © 2022 American Physical Society.
Evolution of collectivity and shape transition in Zn 66
(American Physical Society, 2020) S. Rai; U.S. Ghosh; B. Mukherjee; A. Biswas; A.K. Mondal; K. Mandal; A. Chakraborty; S. Chakraborty; G. Mukherjee; A. Sharma; I. Bala; S. Muralithar; R.P. Singh
Excited states in Zn66 were investigated through the in-beam ?-ray spectroscopic techniques using the Cr52(O18, 2p2n) fusion-evaporation reaction at a beam energy of 72.5 MeV. The ?-rays emitted by the de-exciting nuclei were recorded in coincidence mode using the 14 Compton suppressed Ge clover detectors of the Indian National Gamma Array. With 14 new transitions being identified, the level scheme of Zn66 has been extended up to the excitation energy ˜12.3MeV and spin ˜17?. A rotational band, associated with the two quasineutrons from the 1g9/2 orbital, has been found to exhibit a band crossing with the ground-state band at a spin of 6?. The evolution of the collectivity and shape transition in this nucleus have been discussed in the framework of the total Routhian surface calculations and in comparison with the neighboring Ge68,70 nuclei. © 2020 American Physical Society.
High spin states in 63Cu
(Springer New York LLC, 2018) S. Rai; B. Mukherjee; U.S. Ghosh; A. Biswas; A. Chakraborty; A.K. Mondal; S. Chakraborty; G. Mukherjee; I. Bala; S. Muralithar; R.P. Singh
High-spin states in 63Cu were investigated through in-beam γ-ray spectroscopic techniques using the 52Cr(18O,αp2n) fusion-evaporation reaction at a beam energy of 72.5 MeV. The γ-rays emitted by the excited nucleus were recorded in the coincidence mode using fourteen Compton suppressed Ge clover detectors of the Indian National Gamma-ray Array (INGA). Based on the γ-γ coincidence data, twenty-one new γ-ray transitions have been observed and placed --thereby extending the level scheme of 63Cu up to spin 25 / 2 ℏ and excitation energy ∼ 8. 36 MeV. Shell model calculations are performed in the f5 / 2pg9 / 2 model space with a 56Ni core using two effective interactions, viz. JUN45 and jj44b to interpret the observed excited states of this nucleus. A reasonable agreement is found between the experimental finding and the shell-model calculations --which implies that the excitations within the f5 / 2p3 / 2p1 / 2 orbitals are more dominant in defining the observed level structure than the excitation across the magic shell gap N= Z= 28. © 2018, SIF, Springer-Verlag GmbH Germany, part of Springer Nature.
In-beam spectroscopic study of Zn 63
(American Physical Society, 2019) U.S. Ghosh; S. Rai; B. Mukherjee; A. Biswas; A.K. Mondal; K. Mandal; A. Chakraborty; S. Chakraborty; G. Mukherjee; A. Sharma; I. Bala; S. Muralithar; R.P. Singh
Investigation on the excited states of Zn63 was done through in-beam γ-ray spectroscopic techniques using the Cr52(O18,α3n) fusion-evaporation reaction at a beam energy of 72.5 MeV. Detection of the emitted γ rays from the excited nuclei was performed in the coincidence mode using 14 Compton suppressed Ge clover detectors of the Indian National Gamma Array. Based on the γ-γ coincidence data, 13 new transitions have been placed in the level scheme following their coincidence relationship and intensity balance. Spin and parity assignments of the excited levels have been carried out by extracting the directional correlation from oriented states ratio and polarization asymmetry values of the emitted γ rays. Shell model calculations have been performed in the f5/2pg9/2 model space with a Ni56 core using the jj44bpn interaction, to interpret the observed excited states of the nucleus. A reasonable agreement is found between the experimental findings and the shell-model calculations. In order to understand the evolution of a collective shape built on the 9/2+ (1704 keV) state, we have performed total Routhian surface calculations with a 1g9/2 quasineutron and found reasonable agreement. © 2019 American Physical Society.
Investigation of different possible excitation modes in neutron-rich As 78
(American Physical Society, 2020) A.K. Mondal; A. Chakraborty; K. Mandal; U.S. Ghosh; Aniruddha Dey; Saumyajit Biswas; B. Mukherjee; S. Rai; Krishichayan; S. Chatterjee; S.K. Das; S. Samanta; R. Raut; S.S. Ghugre; S. Rajbanshi; R. Banik; S. Bhattacharyya; S. Nandi; S. Bhattacharya; G. Mukherjee; S. Ali; A. Goswami; R. Chakrabarti; S. Mukhopadhyay; A.K. Sinha; V. Kumar; A. Kumar
The yrast and nonyrast level structure of the odd-odd As78 nucleus has been investigated using the standard ? ray spectroscopic techniques. The excited states of As78 were populated through Ge76(a,pn) fusion evaporation reaction at the incident beam energies of 30, 35, and 40 MeV. The deexciting gamma rays were detected with the Indian National Gamma Array spectrometer composed of Clover and low-energy photon spectrometer detectors. In addition to the extension of the previously known yrast positive-parity band up to Ex ˜ 2.7 MeV with J=11?, an excited dipole band-like structure based on the 7(-), 1243-keV state has also newly been established. Several weak transitions feeding the low-lying nonyrast states have newly been identified and placed in the level scheme. A highly irregular sequence of levels has been observed at the low-excitation regime suggesting the dominance of single-particle excitations. The experimental results have been compared with the predicted results from the large-scale shell-model calculations. The calculated results indicate an enhanced contribution from the intruder p(1g9/2) orbital to the wave function of the positive-parity yrast excited states with J=7?. This enhanced contribution is supposed to provide subsequent mild collectivity for the concerned states. The nature of collectivity has been extracted from the total Routhian surface calculations. Evidences for the possible persistence of the stapler like mechanism prevailing in the positive- and negative-parity level sequences are presented. © 2020 American Physical Society.
Investigation of the low- and medium-spin level structure in As 77
(American Physical Society, 2023) A.K. Mondal; A. Chakraborty; K. Mandal; U.S. Ghosh; Aniruddha Dey; Saumyajit Biswas; B. Mukherjee; Krishichayan; S. Chatteerjee; S.K. Das; S. Samanta; R. Raut; S.S. Ghugre; S. Mukhopadhyay; S. Rajbanshi; R. Banik; S. Bhattacharyya; S. Nandi; S. Chakraborty; S. Bhattacharya; G. Mukherjee; S. Ali; A. Goswami; R. Chakrabarti; A. Kumar; R. Goswami
The low- and medium-spin level structure of As77 nucleus has been investigated using the Ge76(α,p2n) fusion evaporation reaction and the standard in-beam γ ray spectroscopic technique. The deexciting γ rays were detected with the Indian National Gamma Array spectrometer comprising Clover and LEPS detectors. The previously known 9/2+ yrast positive-parity band, based on the π(g9/2) configuration, has been extended to the excitation energy of Ex≈7.5 MeV with Jπ=(33/2+). An extension of the high-lying negative-parity band, based on the π[(g9/2)] - ν[(g9/2)(fp)] configuration, has been made up to Ex≈5.1 MeV, Jπ=(25/2-). The yrast positive-parity α=-1/2 signature partner band has newly been identified and the occurrence of large signature splitting associated with the partner bands have been observed. A quasi-γ vibrational band structure built on the nonyrast 13/2+ state has also newly been established. The experimental findings have been interpreted on the basis of the predicted results from the total Routhian surface, particle plus triaxial-rotor model, and shell-model calculations. The band crossing phenomena correlated to the ν(g9/2) alignment and the perseverance of triaxial shape up to the highest observed excitation regime of the 9/2+ yrast positive-parity band have been discussed. The evidence for the possible onset of the stapler-like mechanism prevailing in the high-lying negative-parity band structure are presented. © 2023 American Physical Society.
Spectroscopic investigation of complex nuclear excitations in Ga 66
(American Physical Society, 2020) U.S. Ghosh; S. Rai; B. Mukherjee; A. Biswas; A.K. Mondal; K. Mandal; A. Chakraborty; S. Chakraborty; G. Mukherjee; A. Sharma; I. Bala; S. Muralithar; R.P. Singh
In-beam spectroscopic technique using the fusion evaporation reaction Cr52(O18,1p3n), at a beam energy of 72.5 MeV, was employed to explore the structural phenomena in Ga66, mainly at intermediate and high spins. The experimental setup involved an array of 14 Compton suppressed Ge clover detectors, placed around the target position to detect emitted γ rays from excited states. A new level scheme has been proposed, which is enriched with more than 20 new transitions and is extended up to an excitation energy ≈12 MeV. A few observed intermediate spin states of Ga66 are discussed in the framework of coupling of single-particle configurations with the vibrational core of Zn64. Shell model calculations have also been performed with two different interactions, viz., jj44bpn and jun45pn, for the interpretation of the observed level structure in Ga66. © 2020 American Physical Society.