Homonuclear ultracold elastic s-wave collisions of alkali atoms via multichannel quantum defect theory

2023/07/31 by Laskowski, Alyson, Mehta, Nirav
#Atomic Physics (physics.atom-ph) #FOS: Physical sciences

paper · doi:10.48550/arxiv.2307.16654

Abstract

Multichannel quantum defect theory (MQDT) provides a powerful toolkit for describing and understanding collisions of cold alkali atoms. Various MQDT approximations differ primarily in how they characterize the so-called short-ranged K-matrix, \mathbf K_sr, which encapsulates the short-ranged, high-energy physics into a handful of low-energy parameters that exhibit simple and smooth dependence on energy and field. Here, we compare three different methods for computing \mathbf K_sr for homonuclear collisions of alkali atoms, from lithium to cesium. The MQDT calculations are benchmarked against numerically converged coupled-channels calculations that use a log-derivative propagator out to the asymptotic region. We study how well these approximations reproduce positions of s-wave magnetic Feshbach resonances, comparing to experiment where possible, and identify the limitations of various approximations.

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