Efficient formation of ground state ultracold molecules via STIRAP from the continuum at a Feshbach resonance

TL;DR

This paper presents a theoretical method using low-intensity laser pulses to efficiently produce ground state ultracold molecules from atomic gases via STIRAP at a Feshbach resonance, achieving high transfer efficiency.

Contribution

It introduces a complete theoretical model for photoassociative STIRAP near Feshbach resonances, enabling nearly complete population transfer with low laser intensities.

Findings

Up to 97% transfer efficiency for a single atom pair.

Up to 70% efficiency averaged over an atomic ensemble.

Optimal laser parameters are 10^2-10^3 W/cm² and several microseconds.

Abstract

We develop a complete theoretical description of photoassociative Stimulated Raman Adiabatic Passage (STIRAP) near a Feshbach resonance in a thermal atomic gas. We show that it is possible to use low intensity laser pulses to directly excite the continuum at a Feshbach resonance and transfer nearly the entire atomic population to the lowest rovibrational level in the molecular ground state. In case of a broad resonance, commonly found in several diatomic alkali molecules, our model predicts a transfer efficiency $\eta$ up to 97% for a given atom pair, and up to 70% when averaged over an atomic ensemble. The laser intensities and pulse durations needed for optimal transfer are $10^2-10^3$ W/cm$^2$ and several $\mu$s. Such efficiency compares to or surpasses currently available techniques for creating stable diatomic molecules, and the versatility of this approach simplifies its potential use for many molecular species.