15min:

N. R. WALKER, G. A. GRIEVES, R. S. WALTERS AND M. A. DUNCAN, University of Georgia, Department of Chemistry, Athens, GA, 30602-2556.

Ni⁺(CO₂)_n and Ni⁺(CO₂)_nAr ion-molecule complexes are produced by laser vaporization in a pulsed nozzle source and studied with mass-selected infrared resonance-enhanced photodissociation spectroscopy (IR-REPD). Photofragment yield is measured as a function of energy in the region of the asymmetric stretch vibration of CO₂ (2349 cm^-1). Fragmentation of Ni⁺(CO₂)_n complexes proceeds by the loss of intact CO₂ units. The mixed clusters fragment by loss of Ar, permitting higher photofragment yields and sharper spectra than those provided by the corresponding pure Ni⁺(CO₂)_n complexes. Spectra for the n\leq4 complexes depict asymmetric stretches to the blue of free CO₂ while solvation effects are observed in the larger complexes. An additional blue-shifted band is observed in complexes with n\geq6, indicating that the Ni⁺ ion participates in a cluster-assisted chemical reaction producing a nickel oxide. This inference is supported by the results of experiments on Ni⁺(O₂)(CO₂)_n complexes, where a blue-shifted band is also observed.