Calculation of the local environment of a barium monofluoride molecule in an argon matrix: A step towards using matrix-isolated BaF for determining the electron electric dipole moment

TL;DR

This paper models the local environment of BaF molecules in an argon matrix, crucial for precision electron EDM measurements, by calculating energetically favored configurations and migration barriers.

Contribution

It provides detailed calculations of the preferred local environment and energy barriers for BaF in argon matrices, aiding electron EDM experimental setups.

Findings

Substitution of BaF for four Ar atoms is most favored.

Large energy barriers fix the molecule's position and orientation at cryogenic temperatures.

Knowledge of the local environment supports precision electron EDM measurements.

Abstract

The local environment of a barium monofluoride (BaF) molecule embedded in an argon matrix is calculated. A substitution of a BaF molecule for four Ar atoms is found to be strongly favoured compared to substitutions for other numbers of Ar atoms. The equilibrium positions of the BaF molecule and its nearby Ar neighbours are found by minimizing the total energy. The potential barrier that prevents the migration of the BaF molecule within the solid and the barrier that prevents its rotation are calculated. At the cryogenic temperatures used by the EDM$^3$ collaboration, these barriers are sufficiently large to fix the position and orientation of the molecule. Knowledge of the local environment of matrix-isolated BaF molecules is essential for the EDM$^3$ collaboration, which is using them in a precision measurement of the electron electric dipole moment.