Nuclear structure of Ac-231

TL;DR

This study investigates the low-energy nuclear structure of Ac-231 using gamma ray spectroscopy, establishing a decay scheme, measuring level half-lives, and providing evidence of weak octupole effects in this exotic nucleus.

Contribution

First detailed decay scheme and level half-life measurements of Ac-231, revealing weak octupole effects in its nuclear structure.

Findings

Decay scheme of 231Ac constructed for the first time

Half-lives of five levels measured using advanced timing methods

Evidence of weak octupole effects in 231Ac

Abstract

The low-energy structure of 231Ac has been investigated by means of gamma ray spectroscopy following the beta-decay of 231Ra. Multipolarities of 28 transitions have been established by measuring conversion electrons with a mini-orange electron spectrometer. The decay scheme of 231Ra --> 231Ac has been constructed for the first time. The Advanced Time Delayed beta-gamma-gamma(t) method has been used to measure the half-lives of five levels. The moderately fast B(E1) transition rates derived suggest that the octupole effects, albeit weak, are still present in this exotic nucleus.