Photoassociation adiabatic passage of ultracold Rb atoms to form ultracold Rb_2 molecules

摘要

We theoretically explore photoassociation by Adiabatic Passage of two colliding cold ^{85}Rb atoms in an atomic trap to form an ultracold Rb_2 molecule in its ground ro-vibrational level. We consider the incoherent thermal nature of the scattering process in a trap and show that coherent manipulations of the atomic ensemble, such as adiabatic passage, are feasible if performed within the coherence time window dictated by the temperature, which is relatively long for cold atoms. By repeating the coherent process many times efficient association of the thermal cloud can be achieved. We show that a sequence of ~2*10^7 pulses of moderate intensities, each lasting ~750 ns, can efficiently photoassociate an entire atomic ensemble at temperature of 100 \muK and density of 10^{11} atoms/cm^3. Use of multiple pathways and multiple pulse sequences makes it easier to populate the target vibrational state.