Photoassociative spectroscopy and formation of cold molecules in cold cesium vapor: Trap-loss spectrum versus ion spectrum

We report on the experimental spectra of all the optically accessible long-range attractive molecular states of the Cs, dimer below the 6s(2)S(1/2) + 6p(2)P(3/2) dissociation limit by molecular photoassociation of cold Cs atoms. The spectra are obtained by the usual trap-loss method as well as by pulsed-laser photoionization of Ca, molecules into Cs: ions. The two spectra present markedly different features. While the 1(g), 0(u)(+), and 0(g)(-) vibrational progressions are present in the trap-loss spectrum, the Cs-2(+) ion spectrum presents only the 0(g)(-) and 1(u) vibrational progressions. Those states (0(g)(-) and 1(u)) lead to the formation of the translationally cold Cs-2 ground state molecules at temperatures in the 100 mu K range, to our knowledge the lowest molecular temperature reported up until now. The C-3 asymptotic coefficients for the 0(u)(+) and 1(g) states are determined through a fit of the experimental energy levels, (C) 1999 Academic Press.