Optical pumping of matrix-isolated barium monofluoride: dependence on the orientation of the BaF molecular axis

TL;DR

This study demonstrates orientation-dependent optical pumping of BaF molecules in a cryogenic neon matrix, revealing that polarization and molecular orientation significantly influence pumping efficiency, which is crucial for eEDM measurements.

Contribution

It shows for the first time that the efficiency of optical pumping of BaF in a matrix depends on molecular orientation and polarization, enabling targeted orientation selection for eEDM experiments.

Findings

Optical pumping efficiency varies with polarization and molecular orientation.

Right-circular polarization yields higher pumping efficiency than left-circular.

The effect is due to interference effects related to molecular orientation.

Abstract

Optical pumping of barium monofluoride (BaF) within a cryogenic neon matrix is demonstrated. Interestingly, with an applied magnetic field of 2~G, optical pumping is found to be considerably more efficient for a laser beam with right-circular polarization compared to left-circular polarization. Calculations show that the higher efficiency is due to a constructive versus destructive interference and is dependent on the orientation of the BaF molecule relative to the magnetic field direction. The effect leads to orientation-dependent optical pumping within the matrix. As optical pumping is the first step used in our planned electron electric-dipole moment (eEDM) measurement, we intend to exploit this property to obtain the selection of molecular orientations that is required for an eEDM measurement.