Multichannel quantum defect theory with a frame transformation for ultracold atom-molecule collisions in magnetic fields

TL;DR

This paper extends multichannel quantum defect theory with a frame transformation to ultracold atom-molecule collisions in magnetic fields, significantly simplifying the quantum dynamics description and reducing computational effort.

Contribution

It introduces an extended formalism that simplifies the complex quantum dynamics of ultracold collisions using fewer parameters and computational resources.

Findings

Achieved a 10^4-fold reduction in computational effort for Mg + NH collisions.

Successfully applied the extended theory to ultracold atom-molecule collisions in magnetic fields.

Provided a practical framework for efficient quantum collision calculations.

Abstract

We extend the powerful formalism of multichannel quantum defect theory combined with a frame transformation to ultracold atom-molecule collisions in magnetic fields. By solving the coupled-channel equations with hyperfine and Zeeman interactions omitted at short range, the extended theory enables a drastically simplified description of the intricate quantum dynamics of ultracold molecular collisions in terms of a small number of short-range parameters. We apply the formalism to ultracold Mg + NH collisions in a magnetic field, achieving a 10$^4$-fold reduction in computational effort.