Cold rubidium molecule formation through photoassociation: A spectroscopicstudy of the 0(g)(-) long-range state of Rb-87(2)

We report the detailed analysis of translationally cold rubidium molecule f ormation through photoassociation. Cold molecules are formed after spontane ous decay of photoexcited molecules from a laser cooled atomic sample, and are detected by selective mass spectroscopy after two-photon ionization int o Rb-2(+) ions. A spectroscopic study of the 0(g)(-)(5S + 5P(3/2)) pure lon g-range state of Rb-87(2) is performed by detecting the ion yield as a func tion of the photoassociation laser frequency the spectral data are theoreti cally analyzed within the semiclassical RKR approach. Molecular ionization is resonantly enhanced through either the 2(3) Pi (g), or the 2(3) Sigma ()(g) intermediate molecular states. Some vibrational levels of the latter e lectronic state are observed and assigned here for the first time. Finally, cold molecules formation rates are calculated and compared to the experime ntally measured ones, and the vibrational distribution of the formed molecu les in the a(3) Sigma (+)(u) ground triplet state is discussed.