Manipulation of Nuclear Isomers with Lasers: Mechanisms and Prospects

TL;DR

This paper reviews the mechanisms behind nuclear isomers, their classifications, and explores the potential of laser manipulation to control these long-lived nuclear states for future applications.

Contribution

It provides a comprehensive overview of nuclear isomer types and discusses prospects for laser-based manipulation of these states, highlighting new avenues for research.

Findings

Different types of nuclear isomers are classified and explained.

Laser techniques could potentially manipulate nuclear isomers.

Understanding isomer mechanisms can lead to novel nuclear applications.

Abstract

Over one hundred years have passed since the nuclear isomer was first introduced, in analogy with chemical isomers to describe long-lived excited nuclear states. In 1921, Otto Hahn discovered the first nuclear isomer $^{234m}$Pa. After that, step by step, it was realized that different types of nuclear isomers exist, including spin isomer, K isomer, seniority isomers, and ``shape and fission'' isomer. The spin isomer occurs when the spin change $\Delta I$ of a transition is very large. The larger $\Delta I$, the lower the electromagnetic transition rates, the longer the half-lives. The K-isomer exists due to the significant change in K, where K is the projection of the total angular momentum on the symmetry axis. The seniority isomers arise due to a very small transition probability in seniority conserving transitions around semi-magic nuclei, where the seniority, which corresponds to the number of unpaired nucleons, is a reasonably pure quantum number. For a so-called shape isomer, the inhibition of the decay transition comes from the associated shape changes. It is caused by that a nucleus is trapped in a deformed shape which is its secondary minimum and is hard to decay back to its ground state.