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

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 ≥ 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 an electric field of less than 20 kV cm(-1).

Efficient method for quantum calculations of molecule-molecule scattering properties in a magnetic field

“…However, not all regimes of molecular collisions are universal, and details of collision dynamics often depend on the intricate interplay between intermolecular and intramolecular interactions at short range. Our work complements recent theoretical efforts [58][59][60] by providing an efficient numerical technique for computing the collision properties of polar molecules for arbitrary collision energies, external field strengths, and interaction potentials. Our proposed methodology can be extended to include the effects of external electric fields, multiple potential energy surfaces and non-adiabatic couplings, and hyperfine interactions, providing a valuable numerical tool for future exploration of molecular collision dynamics in the quantum regime.…”

“…Recent theoretical work on dipolar collisions and chemical reactions of ultracold molecules [58][59][60] began to uncover the universal properties of molecule-molecule scattering in the quantum regime. However, not all regimes of molecular collisions are universal, and details of collision dynamics often depend on the intricate interplay between intermolecular and intramolecular interactions at short range.…”

Perspective: Ultracold molecules and the dawn of cold controlled chemistry

“…244 The opposite effect is observed when the electric field is turned on leading to a suppression of the reactivity. Julienne et al, 245 Zhu et al, 246 and Simoni et al 247 have also examined the stability of ultracold KRb and other heteronuclear dimers of alkali metal atoms in a 1D optical lattice. More recently, Jankowska and Idziaszek 248 presented a formalism to explore ultracold collisions of reactive species in a harmonic trap interacting via an isotropic potential with illustrative results for KRb and LiCs molecules.…”

Long-range interactions between polar alkali-metal diatoms in external electric fields

“…The most spectacular experimental achievements on ultracold dipolar molecular gases have been performed on KRb molecules [8,9,11,19] which motivated a wealth of theoretical investigations on this species [17,[20][21][22][23]. An * maxence.lepers@u-psud.fr accurate description of long-range interactions involving the other heteronuclear alkali diatoms is strongly needed since they draw rising attention [24][25][26][27][28][29][30][31][32]. Considering two identical polar molecules at large distances R (in atomic units 1 a.u.…”