Chemical reactions of ultracold alkaline-earth-metal diatomic molecules

TL;DR

This paper investigates the chemical stability of ultracold alkaline-earth-metal diatomic molecules, revealing that all such molecules can undergo reactions forming homonuclear dimers and trimers, making them inherently chemically unstable at ultralow temperatures.

Contribution

It provides high-level electronic structure calculations showing all heteronuclear combinations are energetically reactive and can form stable complexes, highlighting the need for shielding in experiments.

Findings

Atom-exchange reactions are energetically allowed for all heteronuclear pairs.

Trimer formation is energetically feasible in all dimer collisions.

No energy barriers prevent the studied chemical reactions.

Abstract

We study the energetics of chemical reactions between ultracold ground-state alkaline-earth-metal diatomic molecules. We show that the atom-exchange reactions forming homonuclear dimers are energetically allowed for all heteronuclear alkaline-earth-metal combinations. We perform high-level electronic structure calculations on the potential energy surfaces of all possible homo- and heteronuclear alkaline-earth-metal trimers and show that trimer formation is also energetically possible in collisions of all considered dimers. Interactions between alkaline-earth-metal diatomic molecules lead to the formation of deeply bound reaction complexes stabilized by large non-additive interactions. We check that there are no barriers to the studied chemical reactions. This means that all alkaline-earth-metal diatomic molecules are chemically unstable at ultralow temperature, and optical lattice or shielding schemes may be necessary to segregate the molecules and suppress losses.