Vibrational branching fractions for laser cooling of Sr-containing nonlinear molecules

Paper by Alex and Zack (with collaborator Lan Cheng) has been featured in Editor’s Suggestion on PRA.

The authors explore candidates for a next-generation search for the electron electric dipole moment (eEDM) by experimentally measuring the vibrational loss channels in three Sr-containing nonlinear molecules. They conclude that SrNH2 is the optimal choice for a future laser-cooled molecule-based eEDM experiment.

The vibrational branching fractions from the lowest excited electronic state for SrOCH3, SrNH2, and SrSH are measured at the <0.1% level. Spectra are obtained by driving the X̃−Ã transitions and dispersing the fluorescence on a grating spectrometer. We also perform ab initio calculations for the energies of vibrational levels relevant for laser cooling, as well as branching fractions to support the interpretations of all molecular spectra. Symmetry-group analysis is applied in conjunction with our data to study rotational closure in these molecules. These analyses indicate favorable prospects for laser cooling SrNH2 and other similar alkaline-earth-metal(-like) amides for future beyond the Standard Model physics searches using polyatomic molecules with long-lived parity doublets.