PHOTOFRAGMENTATION DYNAMICS OF $\chem{ICN^{-}(CO_{2})_{n}}$
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Date
2009
Journal Title
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Publisher
Ohio State University
Abstract
We report photofragmentation studies of mass-selected $\chem{ICN^{-}(CO_{2})_{n}}$ ($n$=0-18) cluster anions following 400, 500 and 600 nm excitation. Photodissociation of $\chem{ICN^{-}}$ following excitation $via$ a 500 nm photon results exclusively in an $\chem{I^{-}}$ anionic photoproduct. However, excitation at either 400 nm or 600 nm results in 30\% $\chem{CN^{-}}$ and 70\% $\chem{I^{-}}$ anionic photoproducts. Complexation of $\chem{ICN^{-}}$ with two or more $\chem{CO_{2}}$ molecules opens a third product channel, recombination of the chromophore on the ground state, a channel that is observable at all three photon energies. The product branching ratios for photodissociation of $\chem{ICN^{-}(CO_{2})_{n}}$ show sharp contrast to trends previously observed in dihalide studies of $\chem{IBr^{-}(CO_{2})_{n}}$ and $\chem{I_{2}^{-}(CO_{2})_{n}}$, but are strikingly similar to results found for $\chem{ICl^{-}(CO_{2})_{n}}$. Notably, a peak in the percentage of recombined photoproducts observed as a function of the number of solvent molecules shifts to larger $n$ values as photon energy increases and does not reach 100\% in the first solvation shell. It is likely that an intracluster reaction involving formation of the molecule $\chem{NCCO_{2}^{-}}$ plays a significant role in the dynamics observed following excitation of the $\chem{ICN^{-}(CO_{2})_{n}}$ anion. Supported by NSF and AFOSR
Description
Author Institution: JILA and Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309; Department of Chemistry, The Ohio State University, Columbus, OH 43210