On the formation of van der Waals complexes through three-body recombination

TL;DR

This paper demonstrates that van der Waals molecules can form through three-body recombination in buffer gas cells, with rates influenced by temperature and interaction range, suggesting broad observability of such molecules.

Contribution

It introduces a classical trajectory method to calculate three-body recombination rates for van der Waals molecule formation at low temperatures.

Findings

Formation rates are dominated by long-range interactions at 1-10 K.

Almost any X-RG molecule can be created in buffer gas cells.

Formation rates are similar across different chemical properties of X.

Abstract

In this work, we show that van der Waals molecules X-RG (where RG is the rare gas atom) may be created through direct three-body recombination collisions, i.e., X + RG + RG $\rightarrow$ X-RG + RG. In particular, the three-body recombination rate at temperatures relevant for buffer gas cell experiments is calculated via a classical trajectory method in hyperspherical coordinates [J. Chem. Phys. 140, 044307 (2014)]. As a result, it is found that the formation of van der Waals molecules in buffer gas cells (1 K $\lesssim T \lesssim 10$ K) is dominated by the long-range tail (distances larger than the LeRoy radius) of the X-RG interaction. For higher temperatures, the short-range region of the potential becomes more significant. Moreover, we notice that the rate of formation of van der Walls molecules is of the same order of magnitude independently of the chemical properties of X. As a consequence, almost any X-RG molecule may be created and observed in a buffer gas cell under proper conditions.