First identification of a magnetic rotational band in 190Tl

Snigdha Pal; G. Mukherjee; S. S. Nayak; S. Basu; Shabir Dar; Sneha Das; S. Chakraborty; R. Banik; C. Majumder; R. Palit; P. Dey; A. Kundu; Biswajit Das; Vishal Malik; R. Kumar; S. Rajbanshi; B. S. Naidu; S. K. Jadhav; A. T. Vazhappily

doi:10.1140/epja/s10050-025-01678-3

2024 Impact factor 2.8

Hadrons and Nuclei

Open Access

Eur. Phys. J. A (2025) 61: 205
https://doi.org/10.1140/epja/s10050-025-01678-3

Regular Article - Experimental Physics

First identification of a magnetic rotational band in ¹⁹⁰Tl

Snigdha Pal¹^,2, G. Mukherjee¹^,2^a, S. S. Nayak¹^,2, S. Basu¹^,2, Shabir Dar¹^,2, Sneha Das¹^,2, S. Chakraborty¹^,3, R. Banik³, C. Majumder⁴, R. Palit⁵, P. Dey⁵, A. Kundu⁵, Biswajit Das⁵, Vishal Malik⁵, R. Kumar²^,6, S. Rajbanshi⁷, B. S. Naidu⁵, S. K. Jadhav⁵ and A. T. Vazhappily⁵

¹ Variable Energy Cyclotron Centre, 1/AF Bidhannagar, 700064, Kolkata, India
² Homi Bhabha National Institute, Anushaktinagar, 400094, Mumbai, India
³ Institute of Engineering & Management, Saltlake, 700091, Kolkata, India
⁴ Indian Institute of Technology Bombay, Powai, 400076, Mumbai, India
⁵ Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, 400005, Mumbai, India
⁶ Reactor Physics Design Division, Bhabha Atomic Research Centre, 700085, Mumbai, India
⁷ Department of Physics, Presidency University, 700043, Kolkata, India

^a gopal@vecc.gov.in

Received: 19 April 2025
Accepted: 26 August 2025
Published online: 11 September 2025

Abstract

The excited states of ¹⁹⁰Tl nucleus have been studied experimentally by populating them in the fusion-evaporation reaction ¹⁶⁵Ho(³⁰Si, 5n)¹⁹⁰Tl using 157-MeV beam, delivered from the BARC-TIFR pelletron LINAC facility. The de-excited $γ$ $\gamma$ -rays were detected using the INGA array with 17 Compton-suppressed clover HPGe detectors connected with a digital data acquisition system. A new positive parity band with a sequence of M1 transitions has been observed in ¹⁹⁰Tl and identified as a Magnetic Rotational (MR) band. This band been described under the framework of Semi-Classical Model (SCM). The band is assigned a four quasiparticle configuration $π i_{13 / 2}$ $\pi i_{13/2}$ $\otimes$ $\otimes$ $ν {(i_{13 / 2})}^{- 1} {(p_{3 / 2})}^{- 2}$ $\nu (i_{13/2})^{-1}(p_{3/2})^{-2}$ . Shears mechanism with Principal Axis Cranking (SPAC) model calculations have been performed, which well reproduces the experimentally measured B(M1)/B(E2) values. The Total Routhian Surface calculations suggest a small deformation with non-collective alignment of the angular momentum, corresponding to an oblate shape for the band.

Communicated by Wolfram Korten.

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