Spectroscopy of autoionizing doubly excited states in ultracold Na2 molecules produced by photoassociation -: art. no. 042707

We have performed photoassociation spectroscopy to study the doubly excited states of Na-2 involved in the associative ionization of colliding Na(3 P) atoms. Rovibrational levels of two doubly excited potentials connected to the P-3/2+P-3/2 asymptote, one of O-u(-) and one of 1(u) symmetry, have been identified. These two doubly excited potentials dominate the route to ionization used in photoassociation experiments of cold Na. Binding energies and rotational constants for all the vibrational levels with binding energies <50 GHz have been measured. The asymptotic potentials and short-range ionization probabilities are extracted from the data.