Possibility of shears mechanism due to attractive interaction in the island of $A$ $\sim$ 140 region

TL;DR

This paper explores the potential for shears mechanism bands caused by attractive interactions in nuclei around mass 140, using semi-classical calculations, and suggests experimental validation of predicted transition strengths.

Contribution

It introduces the possibility of attractive interaction-induced shears bands in the A~140 region through HSPAC calculations, expanding understanding of magnetic rotational phenomena.

Findings

Identification of an island in $\

demonstration of the possibility of shears bands due to attractive interactions in A~140 nuclei

Prediction of increasing $B(M1)$ and $B(E2)$ transition strengths with spin in these bands

Abstract

The present work identify an island in the values of dimensionless parameter $\chi$ as +0.10 $<$ $\chi$ $<$ +0.55 outside which no magnetic rotational (MR) bands due to the repulsive interaction would be observed. The semi-classical calculations within the hybrid shears mechanism with the principal axis cranking model (HSPAC) reveal the possibility of the shears band due to the attractive interaction for nuclei in A $\sim$ 140 region. Though the limited information exists in literature, the HSPAC calculation exhibits the dipole bands above the 4389-keV and 4160-keV excited states in $^{145}$Sm and $^{146}$Eu nuclei, respectively, demand their candidature of the attractive shears bands. Other interesting consequence of the HSPAC calculations is the increasing nature of the $B(M1)$ and $B(E2)$ transition strengths with spin unlike the decreasing nature of the transition strengths ($B(M1)$ and $B(E2)$ values) of the MR bands. Thus measurement of the transition probability has been required on urgent basis to validate the strong candidature of such an extreme excitation mechanism in $^{145}$Sm and $^{146}$Eu nuclei.