The chemistry of AlF and CaF production in buffer gas sources

TL;DR

This study investigates chemical reactions in buffer gas sources for AlF and CaF production, revealing that NF3 reacts more efficiently than SF6 and that AlF formation is more probable than CaF across various temperatures.

Contribution

It introduces an ab initio molecular dynamics approach combined with Bayesian inference to analyze reaction mechanisms in buffer gas sources for molecular beam production.

Findings

NF3 reacts more efficiently than SF6 with hot metal atoms.

Reaction products with NF3 have lower kinetic energy, aiding thermalization.

AlF formation probability is higher than CaF across temperatures.

Abstract

In this work, we explore the role of chemical reactions on the properties of buffer gas-cooled molecular beams. In particular, we focus on scenarios relevant to the formation of AlF and CaF via chemical reactions between the Ca and Al atoms ablated from a solid target in an atmosphere of a fluorine-containing gas, in this case, SF6 and NF3. Reactions are studied following an ab initio molecular dynamics approach, and the results are rationalized following a tree-shaped reaction model based on Bayesian inference. We find that NF3 reacts more efficiently with hot metal atoms to form monofluoride molecules than SF6. In addition, when using NF3, the reaction products have lower kinetic energy, requiring fewer collisions to thermalize with the cryogenic helium. Furthermore, we find that the reaction probability for AlF formation is much higher than for CaF across a broad range of temperatures.