Laser spectroscopy and CP-violation sensitivity of actinium monofluoride

TL;DR

This study introduces actinium monofluoride ($^{227}$AcF) as a promising new molecule for highly sensitive CP violation experiments, demonstrating its production, spectroscopy, and potential to vastly improve current constraints.

Contribution

First production and spectroscopic analysis of $^{227}$AcF, showing its suitability for CP violation searches and providing theoretical sensitivity estimates.

Findings

Successfully produced and observed key electronic transition in $^{227}$AcF

Calculated that a near-term experiment could improve CP violation constraints by three orders of magnitude

Demonstrated $^{227}$AcF's potential as a highly sensitive probe for fundamental symmetry violations

Abstract

The apparent invariance of the strong nuclear force under combined charge conjugation and parity (CP) remains an open question in modern physics. Precision experiments with heavy atoms and molecules can provide stringent constraints on CP violation via searches for effects due to permanent electric dipole moments and other CP-odd properties in leptons, hadrons, and nuclei. Radioactive molecules have been proposed as highly sensitive probes for such searches, but experiments with most such molecules have so far been beyond technical reach. Here we report the first production and spectroscopic study of a gas-phase actinium molecule, $^{227}$AcF. We observe the predicted strongest electronic transition from the ground state, which is necessary for efficient readout in searches of symmetry-violating interactions. Furthermore, we perform electronic- and nuclear-structure calculations for $^{227}$AcF to determine its sensitivity to various CP-violating parameters, and find that a realistic, near-term experiment with a precision of 1 mHz would improve current constraints on the CP-violating parameter hyperspace by three orders of magnitude. Our results thus highlight the potential of $^{227}$AcF for exceptionally sensitive searches of CP violation.