In recent years several groups of researchers have succeeded in making samples of cold molecules, at temperatures below 1 K, and of ultracold molecules, at temperatures below 1 mK. We concentrate on the formation of Cs<sub>2</sub> dimers. Starting with laser-cooled atoms, photoassociation forms molecules in an excited electronic state. Various mechanisms are presented for stabilizing these molecules by spontaneous emission into a bound level of the ground electronic state. The design of new formation schemes requires precise knowledge of molecular potential curves that is well beyond the accuracy of <i>ab initio</i> calculations. We show that analytical long-range potentials can be fitted on photoassociation spectra and yield, through the determination of the C<sub>3</sub> long-range coefficient, a value of the radiative lifetime of the 6P<sub>3/2</sub> cesium level with an unprecedented accuracy. For short-range potentials it is possible to avoid explicit calculations by using asymptotic methods that generalize to long-range molecules the quantum-defect concepts developed for Rydberg atoms. Considering two coupled channels, we show how generalized Lu–Fano plots can extract precise information from experimental spectra.
© 2003 Optical Society of America
Olivier Dulieu and Françoise Masnou-Seeuws, "Formation of ultracold molecules by photoassociation: theoretical developments," J. Opt. Soc. Am. B 20, 1083-1090 (2003)