Measuring the nuclear magnetic quadrupole moment in heavy polar molecules

TL;DR

This paper proposes a method to measure the nuclear magnetic quadrupole moment in heavy polar molecules, which can improve constraints on CP-violating parameters related to physics beyond the Standard Model.

Contribution

It introduces a new measurement scheme using superpositions of magnetic sub-levels in molecules to detect the nuclear MQM, enhancing sensitivity to CP violation.

Findings

The energy shifts caused by the MQM can be measured in heavy polar molecules.

The proposed scheme can significantly reduce uncertainties in CP-violating parameters.

A generic preparation method for the required molecular states is developed.

Abstract

Theories that extend the Standard Model of particle physics often introduce new interactions that violate charge-parity (CP) symmetry. CP-violating effects within an atomic nucleus can be probed by measuring its nuclear magnetic quadrupole moment (MQM). The sensitivity of such a measurement is enhanced when using a heavy polar molecule containing a nucleus with quadrupole deformation. We determine how the energy levels of a molecule are shifted by the MQM and how those shifts can be measured. The measurement scheme requires molecules in a superposition of magnetic sub-levels that differ by many units of angular momentum. We develop a generic scheme for preparing these states. Finally, we consider the sensitivity that can be reached, showing that this method can reduce the current uncertainties on several CP-violating parameters.