On the formation of van der Waals molecules in a buffer gas cell

In this work, we study the formation of weakly bound van der Waals molecules X-RG (where RG is the rare gas atom) through direct three-body recombination collisions, i.e., X+ X + RG → X-RG + X. In particular, the three-body recombination rate for 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 ≤ T ≤ 10 K) is dominated by the long-range tail (distances larger than the LeRoy radius) of the X-RG interaction. However, for higher temperatures, the potential short-range region starts to play a more relevant role.