Tuning ultracold collisions of excited rotational dipolar molecules

Gaoren Wang,Goulven Quéméner

doi:10.1088/1367-2630/17/3/035015

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). We can increase or decrease the inelastic and reactive 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, such as elastic and reactive collisions, the inclusion of quadrupole and octopole moments is not important at ultralow energies. The moments are important for processes mediated by state-to-state transitions like inelastic collisions.

Highlights

The recent progresses in the quantum-controlled preparation of dipolar molecules [1] have led to a strong interest in the ultracold scientific community
In this study we propose to use excited rotational states and electric fields to tune the collisional properties of lossy dipolar molecules in free-space, taking fermionic [15] and bosonic
Knowing more on the properties of ground state KRb molecules [36, 37], we included an accurate electronic van der Waals coefficient [29], an absorbing potential to take into account their chemical reactivity [3] and tested the inclusion of electric quadrupole and octopole moments [30]

Summary

INTRODUCTION

The recent progresses in the quantum-controlled preparation of dipolar molecules [1] have led to a strong interest in the ultracold scientific community. If no chemical reactivity is present, the second mechanism (yet not experimentally observed) comes from the possibility for non-reactive molecules to long enough explore the large phase-space density of the moleculemolecule complex. This study is especially relevant for ultracold dipolar molecules produced in their first excited rotational state [17, 18] which are essential to a lot of applications such as tailoring interactions with external fields and confinements [19], suppressing of loss collisions with combination of static electric and microwave fields [20], quantum magnetism with polar molecules [21, 22], dipolar spin-exchange interactions in optical lattices [23, 24] and suppression of molecular loss with continuous quantum Zeno effect [25].

THEORETICAL FORMALISM

RESULTS

CONCLUSION