Formation of Ultracold RbCs Molecules by Photoassociation¹

N. Bouloufa-Maafa^{a, b}, M. Aymar^a, O. Dulieu^a, and C. Gabbanini^c, *

^a Laboratoire Aime Cotton, CNRS, Bât. 505, Univ. Paris-Sud, F-91405 Orsay Cedex, France

^b Université Cergy-Pontoise, 95000 Cergy-Pontoise, France

^c Istituto Nazionale di Ottica, INO-CNR, U.O.S. Pisa “Adriano Gozzini,” Via G.Moruzzi 1, 56124 Pisa, Italy

*e-mail: carlo.gabbanini@ino.it

Received November 9, 2011; in final form, November 15, 2011; published online September 3, 2012

Abstract—The formation of ultracold metastable RbCs molecules is observed in a double species magneto-
optical trap through photoassociation below the ⁸⁵Rb(5S_1/2) + ¹³³Cs(6P_3/2) dissociation limit followed by spon-
taneous emission. The molecules are detected by resonance enhanced two-photon ionization. Using accurate
quantum chemistry calculations of the potential energy curves and transition dipole moment, we interpret the
observed photoassociation process as occurring at short internuclear distance, in contrast with most previous
cold atom photoassociation studies. The vibrational levels excited by photoassociation belong to the 5 th 0⁺ or
the 4 th 0^– electronic states correlated to the Rb(5P_1/2,3/2) + Cs(6S_1/2) dissociation limit. The computed vibra-
tional distribution of the produced molecules shows that they are stabilized in deeply bound vibrational states
of the lowest triplet state. We also predict that a noticeable fraction of molecules is produced in the lowest level
of the electronic ground state.

10.1134/S1054660X12100039

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