A proposed experimental method to determine $\alpha$-sensitivity of splitting between ground and 7.6 eV isomeric states in Th-229

TL;DR

This paper proposes an experimental approach to measure the sensitivity of the Th-229 nuclear transition to variations in the fine-structure constant by comparing atomic transition frequencies in different nuclear states.

Contribution

It introduces a novel experimental method to determine the $eta$-sensitivity of the Th-229 isomeric transition through atomic frequency measurements.

Findings

Method enables extraction of nuclear charge radius differences

Allows estimation of $eta$-dependence of the transition frequency

Provides a pathway to test fundamental physics constants

Abstract

The 7.6 eV electromagnetic transition between the nearly degenerate ground state and first excited state in the Th-229 nucleus may be very sensitive to potential changes in the fine-structure constant, $\alpha = e^2/\hbar c$. However, the sensitivity is not known, and nuclear calculations are currently unable to determine it. We propose measurements of the differences of atomic transition frequencies between thorium atoms (or ions) with the nucleus in the ground state and in the first excited (isomeric) state. This will enable extraction of the change in nuclear charge radius and electric quadrupole moment between the isomers, and hence the $\alpha$-dependence of the isomeric transition frequency with reasonable accuracy.