Cold collisions of N atoms and NH molecules in magnetic fields

TL;DR

This paper investigates cold N atom and NH molecule collisions in magnetic fields, showing favorable conditions for sympathetic cooling but highlighting resonant effects that could hinder the process, with insights into how mass scaling influences scattering.

Contribution

It provides detailed calculations of interaction potentials and explores the impact of reduced mass and shape resonances on collision outcomes for N and NH.

Findings

High elastic-to-inelastic cross section ratios favor sympathetic cooling.

p-wave shape resonance can inhibit cooling in certain isotopic combinations.

Scaling reduced mass affects scattering properties similarly to scaling interaction potential.

Abstract

We calculate the interaction potential between N atoms and NH molecules and use it to investigate cold and ultracold collisions important for sympathetic cooling. The ratio of elastic to inelastic cross sections is large over a wide range of collision energy and magnetic field for most isotopic combinations, so that sympathetic cooling of NH molecules by N atoms is a good prospect. However, there are important effects due to a p-wave shape resonance that may inhibit cooling in some cases. We show that scaling the reduced mass used in the collision is approximately equivalent to scaling the interaction potential. We then explore the dependence of the scattering properties on the reduced mass and explain the resonant effects observed using angular-momentum-insensitive quantum defect theory