Close-coupled model of Feshbach resonances in ultracold $^3$He* and $^4$He* atomic Collisions

TL;DR

This paper develops a close-coupled theoretical model to identify Feshbach resonances in ultracold helium atom collisions, resolving previous conflicting results and revealing new scattering phenomena in heteronuclear systems.

Contribution

The study introduces a new close-coupled model for He* collisions that clarifies the existence of Feshbach resonances and explains previous discrepancies in the literature.

Findings

Several Feshbach resonances were identified in He* collisions.

The existing literature discrepancy was resolved.

A non-Feshbach scattering length variation was observed in heteronuclear collisions.

Abstract

Helium atoms in the metastable $2^3{S_{1}}$ state (He$^*$) have unique advantages for ultracold atomic experiments. However, there is no known accessible Feshbach resonance in He$^*$, which could be used to manipulate the scattering length and hence unlock several new experimental possiblities. Previous experimental and theoretical studies for He$^*$ have produced contradictory results. We aimed to resolve this discrepancy with a theoretical search for Feshbach resonances, using a new close-coupled model of He$^*$ collisions in the presence of an external magnetic field. Several resonances were detected and the existing literature discrepancy was resolved. Although none of the resonances identified are readily experimentally useable, an interesting non-Feshbach scattering length variation with magnetic field was observed in heteronuclear collisions, at field strengths that are experimentally accessible.