paper

Chemistry in a Cryogenic Buffer Gas Cell

arXiv:2501.05613 · doi:10.1021/acs.jpclett.5c02840

Abstract

Cryogenic buffer gas sources are ubiquitous for producing cold, collimated molecular beams for quantum science, chemistry, and precision measurements. The molecules are typically produced by laser ablating a metal target in the presence of a donor gas. The radical of interest emerges due to a barrier-free reaction or under thermal or optical excitation. High-barrier reactions, such as between Ca and H $_{2}$ , should be precluded. We study chemical reactions between Ca and three hydrogen isotopologues H $_{2}$ , D $_{2}$ , and HD in a cryogenic cell with helium buffer gas. We observe that H $_{2}$ can serve as both a reactant and a buffer gas, outperforming D $_{2}$ and HD. We use a reaction network model to describe the chemical dynamics and find that the enhanced molecular yield can be attributed to rapid vibrational excitations of the reactant gas. Our results demonstrate a robust method for generating bright cold beams of alkaline-earth-metal hydrides for laser cooling and trapping.

7+5 pages, 4+5 figures, 1+3 tables