Two-color photoionization spectroscopy of jet-cooled nickelocene

Two-photon ionization of the nickelocene molecules cooled in a supersonic jet was performed for the first time by simultaneous excitation of (eta(5)-C5H5)(2)Ni with two tunable nanosecond dye lasers. The one-photon transition from the HOMO to the Rydberg R4p level was used as the initial step of the multiphoton excitation. In a one-color experiment, the conditions were found for generation of the intact molecular ion, (eta(5)-C5H5)(2)Ni+)2Ni(+), as the only ionic product of the multiphoton ionization. The use of an intense pulse of the second dye laser lead to an increase in the yield of the molecular ion.