# Impact of the ionization of the atomic shell on the lifetime of the $^{229m}$Th isomer

## TL;DR

This paper analyzes how environmental factors like pressure and temperature significantly influence the lifetime of the $^{229m}$Th isomer, highlighting the importance of atomic shell ionization effects on nuclear decay rates.

## Contribution

It provides a detailed analysis of the environmental dependence of the $^{229m}$Th isomer's lifetime and predicts how different ionization states affect decay rates, including a novel theoretical approach.

## Key findings

- Strong dependence of isomer lifetime on environmental conditions.
- Agreement with experimental data for Th$^I$ and Th$^{III}$.
- Prediction of decay rate behavior for Th$^{IV}$ and Th$^{II}$.

## Abstract

Contemporary data are analyzed concerning the half-lives of the $^{229m}$Th isomer in neutral atoms and various ions. It is explicitly shown that the isomer lifetime may strongly depend on the plain environmental physical conditions like pressure and temperature. Calculation is performed on the united platform of interplay of traditional and subthreshold resonance conversion. General agreement with experiment is obtained in the cases of Th$^I$ and Th$^{III}$, a prediction is made concerning Th$^{IV}$. Disagreement with the experiment in the case of Th$^{II}$ may be a consequence of a random very sharp resonance with an electronic level. Account of the influence of the environment on the decay rate helps one to loose the resonance condition, which may lead to agreement with experiment. This will mean the first experimental observation of strong dependence of the nuclear decay rate on the environment.