PHOTOCHEMICAL STUDIES OF CH$_3$OH ISOLATED IN SOLID PARAHYDROGEN
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Date
2012
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Ohio State University
Abstract
Our group is studying the 193.3 nm photochemistry of methanol (CH$_3$OH) isolated in solid pH$_2$ using high-resolution FTIR spectroscopy to explore the low temperature reactions of H-atoms with CH$_3$OH. Gas phase studies have shown that the dominant photodissociation channel is CH$_3$OH + h$\nu$ \rightarrow CH$_3$O + H,\textbf{101}, 5665 (1994).} and thus the {\it in situ} photochemistry is expected to produce methoxy and H-atom radicals. After photolysis the methoxy radicals are immobilized at these temperatures, but the H-atoms can still readily move through solid pH$_2$. For short time 193.3 nm exposures, greater than 90\% of the CH$_3$OH remains intact and therefore repeated FTIR spectra immediately after photolysis can be used to record the kinetics of reactions of H-atoms with CH$_3$OH. We observe exponential growth in the intensities of a number of peaks that can be assigned to the hydroxymethyl CH$_2$OH radical. Further, the growth is bi-exponential and we believe there are two processes that lead to the formation of CH$_2$OH: (1) fast growth by interconversion of CH$_3$O to CH$_2$OH and (2) slow growth due to hydrogen abstraction reactions of cold H-atoms with CH$_3$OH. We have not observed the methoxy radical. Currently we are performing photochemical experiments on fully deuterated methanol (CD$_3$OD) in solid pH$_2$ to test these kinetic interpretations, and the most recent results and analysis will be presented.
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Author Institution: Department of Chemistry, University of Wyoming, Laramie, WY 82071-3838