Search for variation of fundamental constants and violations of fundamental symmetries using isotope comparisons

TL;DR

This paper explores how comparing isotope-based microwave atomic clocks can detect variations in fundamental constants and violations of symmetries by analyzing nuclear magnetic moments and their sensitivities to quark mass changes.

Contribution

It provides detailed calculations of nuclear magnetic moments and their dependence on quark mass variations for isotopes used in experiments, aiding interpretation of fundamental symmetry tests.

Findings

Calculated neutron and proton contributions to nuclear magnetic moments.

Assessed sensitivity of hyperfine transitions to quark mass variation.

Provided insights into interpreting measurements of fundamental symmetry violations.

Abstract

Atomic microwave clocks based on hyperfine transitions, such as the caesium standard, tick with a frequency that is proportional to the magnetic moment of the nucleus. This magnetic moment varies strongly between isotopes of the same atom, while all atomic electron parameters remain the same. Therefore the comparison of two microwave clocks based on different isotopes of the same atom can be used to constrain variation of fundamental constants. In this paper we calculate the neutron and proton contributions to the nuclear magnetic moments, as well as their sensitivity to any potential quark mass variation, in a number of isotopes of experimental interest including 201,199Hg and 87,85Rb, where experiments are underway. We also include a brief treatment of the dependence of the hyperfine transitions to variation in nuclear radius, which in turn is proportional to any change in quark mass. Our calculations of expectation-values of proton and neutron spin in nuclei are also needed to interpret measurements of violations of fundamental symmetries.