Ultracold hydrogen atoms: a versatile coolant to produce ultracold molecules

TL;DR

This paper demonstrates theoretically that ultracold hydrogen atoms are highly effective for sympathetically cooling molecules to microkelvin temperatures due to favorable interaction properties and high elastic-to-inelastic collision ratios.

Contribution

It provides the first detailed quantum collision calculations showing hydrogen's potential as a versatile coolant for ultracold molecules.

Findings

High elastic-to-inelastic collision ratios for H+NH and H+OH.

Shallow and weakly anisotropic potential energy surfaces.

Feasibility of cooling molecules from above 1 K to microkelvin temperatures.

Abstract

We show theoretically that ultracold hydrogen atoms have very favorable properties for sympathetic cooling of molecules to microkelvin temperatures. We calculate the potential energy surfaces for spin-polarized interactions of H atoms with the prototype molecules NH(triplet-Sigma-) and OH(doublet-Pi) and show that they are shallow (50 to 80 cm-1) and only weakly anisotropic. We carry out quantum collision calculations on H+NH and H+OH and show that the ratio of elastic to inelastic cross sections is high enough to allow sympathetic cooling from temperatures well over 1 K for NH and around 250 mK for OH.