Classification of zero-energy resonances by dissociation of Feshbach molecules

TL;DR

This paper investigates how the dissociation of Feshbach molecules under magnetic field sweeps reveals the nature of zero-energy resonances, providing a practical classification method based on atomic kinetic energy distributions.

Contribution

It introduces a new classification approach for zero-energy resonances by analyzing atomic kinetic energy distributions resulting from magnetic field sweeps across Feshbach resonances.

Findings

Distribution peaks indicate closed-channel dominance.

Fast magnetic field changes approximate instantaneous dissociation.

Distribution form in linear ramps is universal under proper conditions.

Abstract

We study the dissociation of Feshbach molecules by a magnetic field sweep across a zero-energy resonance. In the limit of an instantaneous magnetic field change, the distribution of atomic kinetic energy can have a peak indicating dominance of the molecular closed-channel spin configuration over the entrance channel. The extent of this dominance influences physical properties such as stability with respect to collisions, and so the readily measurable presence or absence of the corresponding peak provides a practical method of classifying zero-energy resonances. Currently achievable ramp speeds, e.g. those demonstrated by Duerr et al. [Phys. Rev. A 70, 031601 (2005)], are fast enough to provide magnetic field changes that may be interpreted as instantaneous. We study the transition from sudden magnetic field changes to asymptotically wide, linear ramps. In the latter limit, the predicted form of the atomic kinetic energy distribution is independent of the specific implementation of the two-body physics, provided that the near-resonant scattering properties are properly accounted for.