Speaker
Description
The study of the 1f7/2-shell nuclei gives us a unique opportunity to investigate the interplay between single particle and collective excitations. Strong collectivity near ground state, rotational like band structure, shape transitions towards triaxial and non-collective deformations in the natural (positive for even nuclei and negative for odd nuclei) parity bands have been observed in 48Cr and in a few nuclei around 48Cr and interpret them successfully through shell model calculations [1]. However, the spectroscopic investigations for the unnatural (negative for even nuclei and positive for odd nuclei) parity bands are limited.
The level scheme of the unnatural (positive) parity levels in 49V was extended up to the band terminating state, Jπ = (31/2+). However, the spins and parities of levels above the 11/2+ level were not confirmed and the lifetime data are only available up to the 11/2+ level with large uncertainties (> 100% in some cases) [2]. It was, therefore, felt necessary to re-measure them in order to corroborate the available spectroscopic data and to expand them to include information on high spins.
49V, populated through 48Ti(4He, 2np)49V reaction with 48 MeV 4He beam at VECC Kolkata, was studied very recently by our group using INGA facility, focusing on its natural (negative) parity levels [3]. The present work is an extension to include the results for a few unnatural parity levels. From the analysis, two positive parity signature partner bands were confirmed in 49V and two new γ’s linking these bands were found. In addition, the lifetimes of four levels were measured for the first time, and the lifetimes of two other levels were remeasured to validate our measurements. Multipole mixing ratio (δ) of a few dipole transitions was also measured. Large basis shell model (LBSM) calculations were performed using the code NUSHELLX [4] and SDPFMWPN [5] interaction to interpret the experimental observation. In the calculation only one particle (either proton or neutron) is allowed to excite from the 1d3/2 to the particle restricted pf orbitals. Calculated energies and the transition strengths agreed well with the corresponding experimental values. Based on the measured lifetimes, calculated wave functions and the Qs values, evolution of nuclear shape with angular momentum has been established.
[1] S. M. Lenzi, Phys. Rev. C 56, 1313 (1997); N. H. Medina et. al., Heavy Ion Physics 16, 65 (2002); J. A. Cameron et. al., Phys. Rev. C 58, 808 (1998).
[2] D. Rodrigues et. al., Phys. Rev. C 92, 024323 (2015); B. Haas et. al., Phys. Rev. C 11, 1179 (1975).
[3] Y. Sapkota et al., Phys. Rev. C 105, 044304 (2022).
[4] NuShellX@MSU, B. A. Brown et. al., http://www.nscl.msu.edu/˜brown/resources/resources.html; NuShellX, W. D. M. Rae, http://www.garsington.eclipse.co.uk/.
[5] E. K. Warburton, J. A. Becker, and B. A. Brown, Phys. Rev. C 41, 1147 (1990).
