Characteristics of the 21/2^+ isomer in 93Mo: toward the possibility of enhanced nuclear isomer decay

TL;DR

This paper investigates the structure of the 93Mo 21/2^+ isomer using shell model calculations to understand its decay properties and potential for induced deexcitation in plasma environments.

Contribution

It provides a detailed shell model analysis of the 93Mo isomer, revealing its single-particle configurations and predicting a significant E2 transition for induced decay.

Findings

The isomer has a predominantly single-particle configuration.

The E2 transition to the 17/2^+ state is predicted to be substantial.

The long lifetime is due to neutron-proton interactions affecting energy levels.

Abstract

To discuss whether an enhanced isomer decay is a preferred process in a plasma environment it is required to know the structure of the isomer as well as the nearby states. The spin-21/2, 6.85-hour high-spin isomer in 93Mo is investigated within a shell model which well describes nuclei in this mass region. By using the obtained wave-functions which correctly reproduce the observed B(E2), B(E4), and B(M1) transitions, characteristics of the isomer are shown in comparison with the isomeric states in neighboring nuclei. Calculations suggest that these high-spin isomers are formed with almost pure single-particle-like configurations. The 93Mo 21/2^+ isomer has the predominant configuration $\pi (g_{9/2})^2_{8} \otimes \nu d_{5/2}$ lying below the 15/2^+, 17/2^+, and 19/2^+ states due to neutron-proton interaction, which is the physical origin of its long lifetime. The key E2 transition that connects the 21/2^+ isomer to the upper 17/2^+ level is predicted to be substantial (3.5 W.u), and therefore there is a real prospect for observing induced isomer deexcitation.