Universal ultracold collision rates for polar molecules of two alkali-metal atoms

TL;DR

This paper calculates universal ultracold collision rate constants for heteronuclear alkali-metal dimers, providing insights into reaction dynamics and methods to stabilize ultracold molecules against collisions using electric fields and optical lattices.

Contribution

It introduces universal collision rate calculations for various alkali-metal dimers, including electric field effects and confinement strategies, advancing understanding of ultracold molecular collisions.

Findings

Universal collision rates depend on long-range quantum dynamics.

Electric fields can control and suppress collisional losses.

Confinement in optical lattices stabilizes molecules against reactions.

Abstract

Universal collision rate constants are calculated for ultracold collisions of two like bosonic or fermionic heteronuclear alkali-metal dimers involving the species Li, Na, K, Rb, or Cs. Universal collisions are those for which the short range probability of a reactive or quenching collision is unity such that a collision removes a pair of molecules from the sample. In this case, the collision rates are determined by universal quantum dynamics at very long range compared to the chemical bond length. We calculate the universal rate constants for reaction of the reactive dimers in their ground vibrational state $v=0$ and for vibrational quenching of non-reactive dimers with $v \ge 1$. Using the known dipole moments and estimated van der Waals coefficients of each species, we calculate electric field dependent loss rate constants for collisions of molecules tightly confined to quasi-two-dimensional geometry by a one-dimensional optical lattice. A simple scaling relation of the quasi-two-dimensional loss rate constants with dipole strength, trap frequency and collision energy is given for like bosons or like fermions. It should be possible to stabilize ultracold dimers of any of these species against destructive collisions by confining them in a lattice and orienting them with electric field of less than 20 kV/cm.