Detection by two-photon ionization and magnetic trapping of cold Rb

We present detailed experimental spectra and accurate theoretical interpretation of resonance-enhanced two-photon ionization of ultracold rubidium molecules in the 14000–17000 cm-1 transition energy range. The dimers are formed in a magneto-optical trap by photoassociation followed by radiative decay into the a 3Σu+ lowest triplet state. The theoretical treatment of the process, which reproduces the main features of the spectra, takes into account the photoassociation and decay steps as well as the resonant ionization through the manifold of intermediate gerade states correlated to the 5S + 4D limit. In particular, the energy of the v=1 level of the $(2)\ ^{3}\Sigma_{g}^{+}$ potential well has been determined for the first time. In addition, a tight constraint has been put on the position of the a 3Σu+ repulsive wall. Finally, magnetic trapping of rubidium molecules in the a 3Σu+ state is demonstrated