PHOTODISSOCIATION OF FORMIC ACID ISOLATED IN SOLID PARAHYDROGEN
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Date
2011
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Ohio State University
Abstract
The \textit{in situ} photochemistry of dopant molecules isolated in solid parahydrogen (pH$_2$) typically differs from analogous studies in rare gas crystals for two main reasons: (1) solid pH$_2$ has a negligible cage effect so that photodissociation of a precursor molecule can lead efficiently to well-separated fragments, and (2) radical fragments can potentially react with the pH$_2$ matrix. Our group is currently studying the 193 nm photochemistry of a number of precursor molecules isolated in solid pH$_2$ via high-resolution FTIR spectroscopy. In this talk I will present results for the 193 nm photolysis of formic acid (FA) in solid pH$_2$. In rare gas matrices, the analogous FA photochemistry proceeds via the CO+H$_2$O and CO$_2$+H$_2$ photodissociation channels.$s$\ddot{a}$nen, \textit{J. Mol. Struct. }\textbf{436-437}, 349 (1997).} In solid pH$_2$, in addition to these channels we observe the production of HCO and HOCO. Further, after the UV laser is turned off, the HOCO concentration continues to increase with a slow first-order rate constant for a period of 10 hours. At this point, we still do not have a full explanation of the chemical mechanism leading to the post-photolysis increase in the HOCO concentration.
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Author Institution: Department of Chemistry, University of Wyoming, Laramie, WY 82071-3838