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The Journal of Chemical Physics

Elastic and exchanged atom–molecule collisions in 4He–4He–X (X = 40K, 85Rb, 133Cs) systems at low energy

Huan Zhu, Ningning Gao, Hui-Li Han

Published May 1, 2025• 0 citations
Publisher

Abstract

We investigate the low-energy collision properties of the 4He-4He-X (X = 40K, 85Rb, 133Cs) systems using the R-matrix propagation method within the hyperspherical coordinate framework. The atom-dimer scattering length and atom-molecule collisional exchange rates are derived by solving the three-body Schrödinger equation using a potential energy surface obtained by summing three realistic pairwise potentials. Our results show that the atom-molecule collision exchange rates in the 4He2 + X → 4HeX + 4He process are primarily governed by the 4HeX two-body scattering lengths. Furthermore, when scaled by this parameter, the inelastic cross sections for all three systems collapse onto a single curve, demonstrating universal behavior. These findings provide new insights into the fundamental properties of weakly bound helium-helium-alkali-metal systems and their role in low-energy three-body collisions.

DOI
10.1063/5.0269552

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Differential Faddeev equations in total angular momentum representation are used for the first time to investigate ultra-low energy elastic scattering of a helium atom on a helium dimer. Six potential models of interatomic interaction are investigated. The results improve and extend the Faddeev equations based results known in literature. The employed method can be applied to investigation of different elastic and inelastic processes in three- and four-atomic weakly bounded systems below three-body threshold. 1
We study three-body recombination in the helium-helium-silver system at cold collision energies. The three-body Schr\"odinger equation is solved combining the slow variable discretization and adiabatic approaches with the RRR-matrix propagation method, in order to calculate the product-state-selective total and partial recombination rates in the 4He+4He+^{4}\mathrm{He}+^{4}\mathrm{He} +4He+4He+ Ag system. Recombination at collision energies less than 10 mK is found to take place dominantly to the product molecule 4HeAg^{4}\mathrm{He}\mathrm{Ag}4HeAg in its least bound state, while the three atoms recombine mainly to the 4He2^{4}\mathrm{He}_{2}4He2​ molecule in its ground state at higher collision energies.