First identification of a magnetic rotational band in 190Tl

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 \( \gamma \)-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 \(\pi i_{13/2}\) \(\otimes \) \(\nu (i_{13/2})^{-1}(p_{3/2})^{-2}\). 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.