Radio-Frequency Transitions on Weakly-Bound Ultracold Molecules

TL;DR

This paper demonstrates that radio-frequency spectroscopy is a sensitive method for probing the energy structure and scattering properties of weakly-bound ultracold molecules, with derived lineshapes matching numerical and experimental data.

Contribution

It provides an analytic expression for rf excitation lineshape, revealing dependence on scattering length sign and Fano profiles near Feshbach resonances.

Findings

Lineshape analysis matches experimental data

Bound-free process depends on scattering length sign

Fano profile appears near Feshbach resonances

Abstract

We show that radio-frequency spectroscopy on weakly-bound molecules is a powerful and sensitive tool to probe molecular energy structure as well as atomic scattering properties. An analytic expression of the rf excitation lineshape is derived, which in general contains a bound-free component and a bound-bound component. In particular, we show that the bound-free process strongly depends on the sign of the scattering length in the outgoing channel and acquires a Fano-type profile near a Feshbach resonance. The derived lineshapes provide an excellent fit to both the numerical calculation and the experimental measurements.