15min:

JOSHUA P. MARTIN, QUANLI GU, JOSHUA P. DARR, JILA, Department of Chemistry and Biochemistry University of Colorado at Boulder, Boulder, CO 80309; ANNE B. MCCOY, Department of Chemistry, The Ohio State University, Columbus, OH 43210; AND W. CARL LINEBERGER, JILA, Department of Chemistry and Biochemistry, University of Colorado at Boulder, Boulder, CO 80309.

We report the photoabsorption cross section and photoproduct branching ratios of mass-selected bare \chemICN^- and \chemICN^-(CO₂) following excitation to the A' ² _1/2 electronic excited state. Previous studies of \chemCO₂ solvated-heteronuclear dihalides, \chemIX^-(CO₂)_n (X=Cl, Br), reported three excited state selective classes of photoproducts: \chemI^-, \chemX^-, and \chemIX^- based clusters. Photoabsorption of bare \chemICl^- and \chemIBr^- that leads to population in the A' ² _1/2 state have maxima near 680 nm and 740 nm, respectively, and result in \chemI^- photoproducts exclusively over the entire band corresponding to A' ² _1/2 X ² _1/2 excitation. Interestingly, following excitation of bare \chemICN^- to the comparable state (430-650 nm, maximum at 490 nm), \chemI^- is the dominant ionic photoproduct, but \chemCN^- photoproducts are observed as well. When a single \chemCO₂ solvent molecule is added to \chemICN^-, the same A' ² _1/2 X ² _1/2 excitation results in apparent charge transfer within the complex. Therefore, the observed ionic photoproducts are not just the expected \chemI^- and \chemI^-(CO₂), but \chemCN^- and solvated \chemCN^-(CO₂) photoproducts are also significant products. Analysis of the experimental results using calculated potential energy curves of \chemICN^- reveals intriguing dynamics of the photoexcited triatomic pseudo-dihalide. Supported by NSF and AFOSR.