Accurate calculation of the interaction of a barium monofluoride molecule with an argon atom: A step towards using matrix isolation of BaF for determining the electron electric dipole moment

TL;DR

This paper presents highly accurate calculations of the BaF-Ar interaction potential using advanced relativistic coupled cluster methods, aiding the use of matrix isolation techniques for electron EDM measurements.

Contribution

It provides the first comprehensive relativistic coupled cluster calculations of the BaF-Ar system with extrapolated basis set limits and a fitted interaction potential.

Findings

Calculated interaction energies for BaF-Ar system.

Provided a parametrized potential for BaF-Ar interaction.

Supported the use of matrix isolation for electron EDM experiments.

Abstract

Calculations of the BaF-Ar triatomic system are performed with a relativistic Hamiltonian and coupled cluster theory at the CCSD(T) level for 1386 positions of the Ar atom relative to the BaF molecule. Calculations are repeated with increasing basis sets (double-, triple-, quadruple- and quintuple-zeta), and these are extrapolated to estimate the complete-basis-set limit. The resulting energies provide a potential energy for the interaction of an Ar atom with a BaF molecule. A fit is presented that parametrizes this potential. This work is needed for an understanding of the position, modes of motion and energy shifts of BaF isolated in an Ar matrix. This understanding will guide the EDM$^3$ collaboration in its pursuit of a precision measurement of the electron electric dipole moment using BaF isolated in a cryogenic Ar matrix.