Extremely asymmetric shears band in 143Sm

TL;DR

This paper reports the discovery of an extremely asymmetric shears band in 143Sm, characterized by a high number of quasiparticles and significant core rotation contribution, expanding understanding of magnetic rotation phenomena at high quasiparticle excitations.

Contribution

It presents the first observation of a shears band with nine quasiparticles and high asymmetry, analyzed through SPAC model calculations, revealing new insights into magnetic rotation at quasiparticle limits.

Findings

Maximum quasiparticles in a shears band observed

Significant core rotation contribution identified

Unique asymmetric shears band in 143Sm characterized

Abstract

A dipole sequence has been observed and investigated in the 143 Sm nucleus populated through the heavy-ion induced fusion-evaporation reaction and studied using the Indian National Gamma Array (INGA) as the detection system. The sequence has been established as a Magnetic Rotation (MR) band primarily from lifetime measurements of the band members using the Doppler Shift Attenuation Method (DSAM). A configuration based on nine quasiparticles, with highly asymmetric angular momentum blades, has been assigned to the shears band in the light of the theoretical calculations within the framework of Shears mechanism with the Principal Axis Cranking (SPAC) model. This is hitherto the maximum number of quasiparticles along with the highest asymmetricity associated with a MR band. Further, as it has followed from the SPAC calculations, the contribution of the core rotation to the angular momentum of this shears band is substantial and greater than in any other similar sequence, at least in the neighbouring nuclei. This band can thus be perceived as a unique phenomenon of shears mechanism in operation at the limits of quasiparticle excitations, as manifested in MR band-like phenomena, evolving into collectivity.