Photoinduced Electron Transfer and Solvation in Iodide-doped Acetonitrile Clusters†

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• 作者：Oli T. Ehrler ; Graham B. Griffin ; Ryan M. Young ; Daniel M. Neumark*
• 刊名：Journal of Physical Chemistry B
• 出版年：2009
• 出版时间：April 2, 2009
• 年：2009
• 卷：113
• 期：13
• 页码：4031-4037
• 全文大小：180K
• 年卷期：v.113,no.13(April 2, 2009)
• ISSN：1520-5207

文摘

We have used ultrafast time-resolved photoelectron imaging to measure charge transfer dynamics in iodide-doped acetonitrile clusters I⁻(CHb>3b>CN)b>nb> with n = 5−10. Strong modulations of vertical detachment energies were observed following charge transfer from the halide, allowing interpretation of the ongoing dynamics. We observe a sharp drop in the vertical detachment energy (VDE) within 300−400 fs, followed by a biexponential increase that is complete by 10 ps. Comparison to theory suggests that the iodide is internally solvated and that photodetachment results in formation of a diffuse electron cloud in a confined cavity. We interpret the initial drop in VDE as a combination of expansion of the cavity and localization of the excess electron on one or two solvent molecules. The subsequent increase in VDE is attributed to a combination of the I atom leaving the cavity and rearrangement of the acetonitrile molecules to solvate the electron. The n = 5−8 clusters then show a drop in VDE of around 50 meV on a much longer time scale. The long-time VDEs are consistent with those of (CHb>3b>CN)b>nb>⁻ clusters with internally solvated electrons. Although the excited-state created by the pump pulse decays by emission of a slow electron, no such decay is seen by 200 ps.