Molecular states near a collision threshold

TL;DR

This paper reviews the properties of near-threshold molecular states formed from ultracold atoms, emphasizing quantum defect theory and multichannel approaches for different isotopes and molecules.

Contribution

It provides a comprehensive characterization of near-threshold molecular states using quantum defect theory and extends it to multichannel scenarios for Feshbach and photoassociation resonances.

Findings

Characterization of molecular states for different isotopes of Yb_2.

Application of multichannel theory to Feshbach and photoassociation resonances.

Examples demonstrating the theory's relevance to ultracold molecule formation.

Abstract

This chapter summarizes the properties of near-threshold molecular states that can be formed from ultracold atoms. The properties of the states for a single potential are characterized for different partial waves using the concepts of quantum defect theory for a van der Waals potential. Examples are given for various isotopes of the Yb_2 molecule. Magnetically tunable Feshbach resonances or photoassociation resonances are characterized by the multichannel version of the theory. Examples of the latter are given for the KRb molecule.