Browsing by Author "Aniruddha Dey"

Now showing 1 - 3 of 3

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.
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.