The γ-ray spectroscopy studies of low-spin structures in ²¹⁰Bi and ²⁰⁶Tl using cold neutron capture reactions

¹ Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Kraków, Poland
² INFN Sezione di Milano and Università degli Studi di Milano, Via Celoria 16, 20133 Milano, Italy
³ Dipartimento di Fisica e Astronomia dell’Università and INFN Sezione di Padova, I-35131 Padova, Italy
⁴ Institut Laue-Langevin, 71 avenue des Martyrs, 38042 Grenoble Cedex 9, France
⁵ GANIL, Bd. Becquerel, BP 55027, 14076 CAEN Cedex 05, France
⁶ Institut für Kernphysik, TU Darmstadt, Schlossgartenstr. 9, D-64289 Darmstadt, Germany
⁷ LPSC, Université Joseph Fourier Grenoble 1, CNRS/IN2P3, Institut National Polytechnique de Grenoble, F-38026 Grenoble Cedex, France
⁸ ELI-NP, Horia Hulubei National Institute for Physics and Nuclear Engineering, 30 Reactorului Street, RO-077125 Bucharest-Magurele, Romania
⁹ Faculty of Physics, University of Warsaw, ul. Pasteura 5, PL-02-093, Warszawa, Poland

^* e-mail: natalia.cieplicka@ifj.edu.pl

Published online: 14 November 2018

Abstract

The γ-coincidence studies of low-spin structures of ²¹⁰Bi and ²⁰⁶Tl are presented. The ²¹⁰Bi nucleus, populated in thermal neutron capture reaction, was investigated using EXILL HPGe array at Institut Laue-Langevin in Grenoble. The experimental results were compared to the shell-model calculations allowing to draw the conclusions on the nature of the low-spin excitations populated below the neutron binding energy in ²¹⁰Bi (4.6 MeV). It has been found that some levels cannot be described by the valence proton and neutron couplings, but may arise from couplings of valence particles to the 3^- octupole phonon of the doubly magic ²⁰⁸Pb core. Moreover, preliminary results of a low-spin structure measurements of ²⁰⁶Tl by the γ-coincidence technique, making use of the ²⁰⁵Tl(n,γ)206Tl reaction at the FIPPS prompt γ-ray spectroscopy facility of ILL are shown. The population of a large number of excited states of ²⁰⁶Tl above the ground state up to the neutron binding energy (at 6.5 MeV), within a few units of spin is expected. The analysis involving double and triple γ-coincidences and γγ-angular correlations will allow to significantly extend the experimental information on the energy and spin-parity of the levels in ²⁰⁶Tl. This will help shedding light on the proton-hole and neutron-hole couplings near the doubly magic core ²⁰⁸Pb.