Spectroscopy of autoionizing doubly excited states in ultracold Na-2 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 bee n identified. These two doubly excited potentials dominate the route to ion ization used in photoassociation experiments of cold Na. Binding energies a nd rotational constants for all the vibrational levels with binding energie s <50 GHz have been measured. The asymptotic potentials and short-range ion ization probabilities are extracted from the data.