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 η 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 102−103
W/cm2 and several μs. 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