Measuring the nuclear magnetic quadrupole moment in heavy polar molecules

Abstract

Theories that extend the Standard Model of particle physics often introduce new interactions that violate charge-parity (CP) symmetry. Charge-parity-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 magnetic quadrupole moment 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 charge-parity-violating parameters.

Measuring the nuclear magnetic quadrupole moment of optically trapped ytterbium atoms in the metastable state

“…Importantly, the MQM is enhanced in some heavily deformed nuclei, as has been confirmed using spherical basis calculations [15,18] and Nilsson model calculations [16]. While there are several nuclei that can be used for MQM measurements, including some radioactive nuclei, there has been considerable interest in the stable isotope 173 Yb, which has I = 5/2 and large quadrupole deformation that leads to huge enhancement of the MQM [19,20]. This fact has led to experimental proposals to measure the MQM using molecules like YbF [20] and YbOH [21,22], exploiting the internal magnetic field gradient induced by the electric field in polarized molecules.…”

“…While there are several nuclei that can be used for MQM measurements, including some radioactive nuclei, there has been considerable interest in the stable isotope 173 Yb, which has I = 5/2 and large quadrupole deformation that leads to huge enhancement of the MQM [19,20]. This fact has led to experimental proposals to measure the MQM using molecules like YbF [20] and YbOH [21,22], exploiting the internal magnetic field gradient induced by the electric field in polarized molecules. Recently, MQM measurements using solids containing deformed nuclei have also been proposed [23][24][25].…”