Multiphoton double ionization of barium

The multiphoton double ionization of Ba from approximately 280 to 700 nm was investigated using laser pulses 5 ns long of peak intensity approximately 10/sup 10/ W/cm/sup 2/. The spectrum consists of a number of strong resonances, which can be assigned to Ba/sup +/ transitions. Most of the assignments have been verified by pump-probe techniques. Thus, the Ba/sup ++/ observed is due to sequential ionization. The multiphoton ionization probability is highest for lambda approximately 500 nm, which matches a series of strong Ba and Ba/sup +/ transitions leading to double ionization.<
>