The prospects for producing ultracold NH$_3$ molecules by sympathetic cooling: a survey of interaction potentials

TL;DR

This study assesses the feasibility of producing ultracold NH3 molecules via sympathetic cooling with various ultracold atoms by analyzing their interaction potentials and energy surfaces.

Contribution

It provides detailed ab initio potential energy surfaces and Van der Waals coefficients for NH3 interactions with selected atoms, highlighting the challenges for sympathetic cooling.

Findings

Deep potential wells and strong anisotropies in alkali-metal and alkaline-earth systems.

Weak binding and less anisotropy in Xe-NH3 interactions.

Sympathetic cooling likely requires molecules and atoms in their lowest internal states.

Abstract

We investigate the possibility of producing ultracold NH3 molecules by sympathetic cooling in a bath of ultracold atoms. We consider the interactions of NH3 with alkali-metal and alkaline-earth atoms, and with Xe, using ab initio coupled-cluster calculations. For Rb-NH3 and Xe-NH3 we develop full potential energy surfaces, while for the other systems we characterize the stationary points (global and local minima and saddle points). We also calculate isotropic and anisotropic Van der Waals C6 coefficients for all the systems. The potential energy surfaces for interaction of NH3 with alkali-metal and alkaline-earth atoms all show deep potential wells and strong anisotropies. The well depths vary from 887 1/cm for Mg-NH3 to 5104 1/cm for Li-NH3. This suggests that all these systems will exhibit strong inelasticity whenever inelastic collisions are energetically allowed and that sympathetic cooling will work only when both the atoms and the molecules are already in their lowest internal states. Xe-NH3 is more weakly bound and less anisotropic.