Quantum Defect Theory description of weakly bound levels and Feshbach resonances in LiRb

TL;DR

This paper applies multichannel quantum defect theory combined with frame transformation to accurately model Fano-Feshbach resonances and bound states in LiRb isotopes, providing a compact and effective description of these phenomena.

Contribution

The study demonstrates that MQDT with FT can accurately predict Feshbach resonances and bound states in LiRb, matching results from more complex numerical methods.

Findings

MQDT accurately models Feshbach resonances in LiRb.

MQDT provides a compact description of photoassociation observables.

Results confirm MQDT's effectiveness comparable to fully numerical solutions.

Abstract

The multichannel quantum defect theory (MQDT) in combination with the frame transformation (FT) approach is applied to model the Fano-Feshbach resonances measured for $^{7}$Li$^{87}$Rb and $^{6}$Li$^{87}$Rb [Marzok {\it et al.} Phys. Rev. A {\bf 79} 012717 (2009)]. The MQDT results show a level of accuracy comparable to that of previous models based on direct, fully numerical solutions of the the coupled channel Schr\"odinger equations (CC). Here, energy levels deduced from 2-photon photoassociation spectra for $^{7}$Li$^{85}$Rb are assigned by applying the MQDT approach, obtaining the bound state energies for the coupled channel problem. Our results confirm that MQDT yields a compact description of photoassociation observables as well as the Fano-Feshbach resonance positions and widths.