Dissertation Defense: Toshihiko Shimasaki, Yale University, “Continuous Production of 85Rb133Cs Molecules in the Rovibronic Ground State via Short-Range Photoassociation”

We present our results on continuous production of ultracold ^{85}Rb^{133}Cs molecules in the rovibronic ground state via short-range photoassociation (PA). Starting with ultracold Rb and Cs atoms trapped in dual-species dark-SPOT MOT, we photoassociate a pair of Rb and Cs atoms into an excited molecular state, which decays into the electronic ground state by spontaneous emission. We apply depletion spectroscopy to the RbCs system and establish a rotationally-resolved, state-selective detection method for molecules in the vibronic ground state X^1S+(v = 0). With this technique, we verified molecule production in the rovibronic ground state X^1S+(v = J = 0). We explored a variety of short-range PA pathways, namely, via excitation to the 2^3P_0+ and 2^3P_0- states, the 2^1P_1-2^3P_1-3^3S^+_1 complex, and the b^3P_1^c^3S^+_1-B^1P_1 complex. One of the b^3P_1^c^3S^+_1-B^1P_1 complex of states, with PA frequency 10151.24 cm^-1, was found to be the most efficient pathway so far. Using PA through this state, we achieved a molecule production rate of up to 8000 molecules /s in X1^S+(v = J = 0). This opens up the possibility of utilizing short-range PA for preparing a large sample of ultracold, rovibronic ground state molecules via continuous accumulation.