Antimagnetic rotation and sudden change of electric quadrupole transition strength in 143Eu

TL;DR

This study investigates antimagnetic rotation in 143Eu by measuring state lifetimes and polarization, revealing a sudden change in quadrupole transition strength linked to shears configuration crossing, supported by semi-classical modeling.

Contribution

It provides the first experimental evidence of a sudden increase in B(E2) values after band crossing in 143Eu, indicating a new shears re-opening phenomenon in antimagnetic rotation.

Findings

Decreasing B(E2) with spin confirms antimagnetic rotation.

Abrupt B(E2) increase after band crossing suggests shears re-opening.

Results align with semi-classical geometric model calculations.

Abstract

Lifetimes of the states in the quadrupole structure in 143Eu have been measured using the Doppler shift attenuation method as well as parity of the states in the sequence has been firmly identified from polarization measurement using the Indian National Gamma Array. The decreasing trends of the deduced quadrupole transition strength B(E2) with spin, along with increasing J (2) /B(E2) values before band crossing, conclusively establish the origin of these states as arising out of antimagnetic rotation. The abrupt increase in the B(E2) values after the band crossing in the quadrupole band, a novel feature observed in the present experiment, may indicates the crossing of different shears configurations resulting in re-opening of shears structure. The results are well reproduced by numerical calculation within the framework of semi-classical geometric model.