Tuning ultracold collisions of excited rotational dipolar molecules

TL;DR

This paper demonstrates how electric fields can precisely tune collision rates of excited dipolar molecules like KRb at ultracold temperatures, revealing control over loss and elastic processes.

Contribution

It introduces a method to sharply tune ultracold molecular collision rates using electric fields and includes higher multipole moments in the interaction model.

Findings

Electric fields can control collision rates in excited dipolar molecules.

Higher multipole moments are significant for inelastic collision processes.

Tuning affects both bosonic and fermionic molecules similarly.

Abstract

We investigate the ultracold collisions of rotationally excited dipolar molecules in free-space, taking the hetero-nuclear bi-alkali molecule of KRb as an example. We show that we can sharply tune the elastic, inelastic and reactive rate coefficients of lossy molecular collisions when a second rotationally excited colliding channel crosses the threshold of the initial colliding channel, with the help of an applied electric field, as found by Avdeenkov et al. for non-lossy molecules [Phys. Rev. A 73, 022707 (2006)]. We can increase or decrease the loss processes whether the second channel is above or below the initial channel. This is seen for both bosonic and fermionic molecules. Additionally, we include the electric quadrupole and octopole moment to the dipole moment in the expression of the long-range multipole-multipole interaction. We found that for processes mediated by the incident channel like elastic and loss collisions, the inclusion of quadrupole and octopole moments are not important at ultralow energies. They are important for processes mediated by state-to-state transitions like inelastic collisions.