Molecular dissociation by mid-IR femtosecond pulses

By focusing a MIR femtosecond laser in a cell containing gas-phase metal carbonyls, the resonant infrared multiphoton dissociation of molecules was observed, Cr(CO)(6), Mo(Co)(6), W(CO)(6), and Fe(CO)(5), could easily be dissociated, which requires an excitation to at least v = 7 or 8 of the CO stretch vibration, After irradiation with similar to150 fs pulses at 5 mum the metal carbonyl practically disappears in favor of free CO, as detected by the IR spectrum. By comparing the power dependence of the total conversion with a model, we can infer that only few vibrational degrees of freedom are involved in the excitation process. (C) 2002 Published by Elsevier Science B.V.