Formation of van der Waals molecules in buffer gas cooled magnetic traps

TL;DR

This paper demonstrates the formation of helium-containing cold polar molecules in buffer gas cooled magnetic traps, investigates their spin relaxation mechanisms, and explains observed thermal spin change dependence.

Contribution

It provides evidence for molecular formation in buffer gas traps and links spin relaxation to Landau-Zener transitions caused by hyperfine interactions.

Findings

High-density formation of helium-containing molecules in cryogenic buffers

Identification of Landau-Zener transitions as a spin relaxation mechanism

Explanation of T^6 thermal dependence of spin change in silver molecules

Abstract

We show that a large class of helium-containing cold polar molecules form readily in a cryogenic buffer gas, achieving densities as high as 10^12 cm^-3. We explore the spin relaxation of these molecules in buffer gas loaded magnetic traps, and identify a loss mechanism based on Landau-Zener transitions arising from the anisotropic hyperfine interaction. Our results show that the recently observed strong T^6 thermal dependence of spin change in buffer gas trapped silver (Ag) is accounted for by the formation and spin change of AgHe, thus providing evidence for molecular formation in a buffer gas trap.