Observation of multiple doubly degenerate bands in Tl-195

The High-spin states in 195Tl, populated through the 185,187Re(13C, xn) fusion evaporation reaction at the beam energy of 75 MeV, were studied using the Indian National Gamma Array (INGA). More than 50 new γ transitions have been placed in the proposed level scheme which is extended up to the excitation energy of ≈ 5.6 MeV and spin. Two pairs of degenerate bands based on two different quasi-particle configurations have been identified in this nucleus indicating the first observation of such bands in an odd-A nucleus in region and signify the first evidence of multiple chiral bands in a nucleus in this region. The total Routhian surface calculations predict triaxial shapes for both the configurations and thereby, support the experimental observation. The importance of multiple neutron holes in the orbital and the stability of shapes for these two configurations have been discussed.Financial support of Department of Science & Technology, Govt. of India for clover detectors of INGA (Grant No. IR/S2/PF-03/2003-II) is greatfully acknowledged. One of the authors (S. Bhattacharya) acknowledges with thanks the financial support received as Raja Ramanna Fellowship from the Department of Atomic Energy, Govt. of India. T.R and Md. A.A acknowledge with thanks the financial support received as research fellows from the Department of Atomic Energy (DAE), Govt. of India

Effect of neutron alignments on the structure of Tl 197

The excited states of 197Tl have been studied via 19 Au(4He, 4n)197 Tl reaction at a beam energy of 50 MeV from the K-130 cyclotron at the Variable Energy Cyclotron Centre (VECC). The γ rays were detected using the VECC array for Nuclear Spectroscopy (VENUS) with six Compton-suppressed clover HPGe detectors. An improved level scheme of 197 Tl has been proposed from this work, which has been extended to 5.1 MeV of excitation energy and 39/2 ℏ of spin from the placement of 28 new γ-ray transitions. Band crossings in the known one- and three-quasiparticle (qp) bands have been identified for the first time in this work. Two new bands, based on 3-qp and 5-qp configurations, have been observed for the first time in this nucleus; both of which are identified as the magnetic rotational (MR) in nature. The excitation energies of these bands are similar to that of the doubly degenerate bands observed for the similar 3-qp and 5-qp configurations in 195 Tl. These indicate a transition from an aplanar geometry of the neutron, proton, and the core angular momentum vectors to a planar one for neutron number N≥116 in Tl isotopes. The total Routhian surface calculations suggest a change in shape from oblate for the 1-qp configuration to a near-spherical one for the 3- and 5-qp configurations. This is consistent with the observed MR nature of the bands with multi-qp configuration. The MR bands are well reproduced by a model calculations in the frame work of the shears mechanism with the principal axis cranking.One of the authors (H.P.) is grateful for the support from the Ramanujan Fellowship Research Grant under SERB-DST Grant No. SB/S2/RJN-031/2016

Observation of multiple doubly degenerate bands in ¹⁹⁵Tl

The High-spin states in 195 Tl, populated through the 185,187 Re( 13 C, xn) fusion evaporation reaction at the beam energy of 75 MeV, were studied using the Indian National Gamma Array (INGA). More than 50 new γ transitions have been placed in the proposed level scheme which is extended up to the excitation energy of ≈ 5.6 MeV and spin =22.5ħ . Two pairs of degenerate bands based on two different quasi-particle configurations have been identified in this nucleus indicating the first observation of such bands in an odd- A nucleus in A∼190 region and signify the first evidence of multiple chiral bands in a nucleus in this region. The total Routhian surface calculations predict triaxial shapes for both the configurations and thereby, support the experimental observation. The importance of multiple neutron holes in the i13/2 orbital and the stability of shapes for these two configurations have been discussed.Financial support of Department of Science & Technology, Govt. of India for clover detectors of INGA (Grant No. IR/S2/PF-03/2003-II) is greatfully acknowledged. One of the authors (S. Bhattacharya) acknowledges with thanks the financial support received as Raja Ramanna Fellowship from the Department of Atomic Energy, Govt. of India. T.R and Md. A.A acknowledge with thanks the financial support received as research fellows from the Department of Atomic Energy (DAE), Govt. of India

Decay measurements of 43K(β−)43Ca by HRS and TAS

In this work, decay spectroscopy of neutron-rich 43K has been performed at the Radioactive Ion Beam (RIB) facility at Variable Energy Cyclotron Centre (VECC), Kolkata by producing it with an 18-MeV alpha beam on 40Ar gas target. The beam was delivered from the K130 Cyclotron and the gas jet recoil transport system was used to move the products to a low-background site. The β-feeding intensities were measured by both high resolution γ-ray spectroscopy and total absorption γ-ray spectroscopy methods in order to address mainly the anomalies (if any) in the feeding to ΔJ ≥ 1 levels reported earlier. The decay half-life of 43K was also measured to be 22.4(1) hrs

Decay measurements of

In this work, decay spectroscopy of neutron-rich 43K has been performed at the Radioactive Ion Beam (RIB) facility at Variable Energy Cyclotron Centre (VECC), Kolkata by producing it with an 18-MeV alpha beam on 40Ar gas target. The beam was delivered from the K130 Cyclotron and the gas jet recoil transport system was used to move the products to a low-background site. The β-feeding intensities were measured by both high resolution γ-ray spectroscopy and total absorption γ-ray spectroscopy methods in order to address mainly the anomalies (if any) in the feeding to ΔJ ≥ 1 levels reported earlier. The decay half-life of 43K was also measured to be 22.4(1) hrs