Free-bound excitation and predissociation of ytterbium dimers near the atomic transition

A continuous excitation band of a free-bound photoassociation transition of ytterbium atoms is observed as a red wing of the atomic line at 399 nm for a hot thermal vapor. The excitation to the molecular state is observed by monitoring fluorescence from the state atoms, which allows us to detect the production of molecules with high sensitivity. The photoassociation is characterized in comparison with transitions to atomic Rydberg states. The time profile of the fluorescence signal suggests that the molecular state predissociates with states correlating to the atomic states.