SPECTROSCOPY AND DYNAMICS OF EXCITED HARPOONING REACTIONS - THE PHOTODEPLETION ACTION SPECTRUM OF THE BA-CENTER-DOT-CENTER-DOT-CENTER-DOT-FCH3 COMPLEX

A laser time-of-flight mass spectrometer setup used to investigate the spectroscopy and dynamics of weakly bound complexes is described. Com plexes were produced by laser vaporization of metals into a supersonic expansion of helium and a solvent. The first results consisting of la ser ionization and photodepletion spectra of Ba ...(FCH3)(n) for 1 les s than or equal to n less than or equal to 3 are reported. The measure ment of the Ba ... FCH3+ signal as a function of the ionization photon energy allowed estimation of the complex ionization potential, which was found to be 4.5 +/- 0.1 eV. The photodepletion spectrum of the Ba ... FCH3 complex displayed two distinct regions. At longer wavelengths it showed a high cross-section (60-70 Angstrom(2)) and a well-defined vibrational structure, while a much smaller cross-section (2-4 Angstr om(2)), with a more diffuse structure, appeared at shorter wavelengths . In addition, clear resonances were observed at longer wavelengths, i ndicating a significant coupling between the bound excited potential o f the complex and the (open channel) ionic potential leading to BaF CH3 reaction products. All of these features are discussed, taking in to account the interplay between the spectroscopy and dynamics associa ted with each electronically excited state of the complex that governs the photoinitiated harpooning reaction.