15min:

T. JAEGER, R. S. WALTERS AND M. A. DUNCAN, University of Georgia, Department of Chemistry, Athens, GA, 30602- 2556.

Metal ion-acetylene complexes of the general form M⁺-(C₂H₂)_n are synthesized in the gas phase by a pulsed nozzle laser ablation cluster source. These ions are then mass selected in a reflectron time-of-flight mass spectrometer where they are excited and undergo multiphoton absorption from a tunable infrared OPO/OPA laser system. Efficient fragmentation occurs by the loss of whole C₂H₂ units and this process is enhanced on vibrational resonances near the symmetric and asymmetric C-H stretch frequencies of acetylene. Infrared photofragmentation spectra are obtained by monitoring the fragment yield versus energy of the tunable infrared laser in the 3000 cm^-1 to 3400 cm^-1 region. the observed infrared band positions are red-shifted from those of free acetylene consistent with the weakening of the carbon-carbon bond energy by electron withdrawal. Interpretation of the spectra for M⁺ = Ni⁺ and Co⁺ will be discussed.