Influence of a Feshbach resonance on the photoassociation of LiCs

TL;DR

This study investigates how a Feshbach resonance influences the photoassociation process of ultracold LiCs molecules, revealing that hyperfine couplings and resonances significantly enhance molecule formation rates.

Contribution

It provides a detailed coupled-channel model showing the impact of a Feshbach resonance on photoassociation rates and the formation of ground state molecules.

Findings

Large photoassociation rate constants at high detunings.

Enhancement caused by triplet component echo in scattering wave function.

Feshbach resonance induces significant coupling effects.

Abstract

We analyse the formation of ultracold 7Li133Cs molecules in the rovibrational ground state through photoassociation into the B1Pi state, which has recently been reported [J. Deiglmayr et al., Phys. Rev. Lett. 101, 133004 (2008)]. Absolute rate constants for photoassociation at large detunings from the atomic asymptote are determined and are found to be surprisingly large. The photoassociation process is modeled using a full coupled-channel calculation for the continuum state, taking all relevant hyperfine states into account. The enhancement of the photoassociation rate is found to be caused by an `echo' of the triplet component in the singlet component of the scattering wave function at the inner turning point of the lowest triplet a3Sigma+ potential. This perturbation can be ascribed to the existence of a broad Feshbach resonance at low scattering energies. Our results elucidate the important role of couplings in the scattering wave function for the formation of deeply bound ground state molecules via photoassociation.