FTIR studies of the photochemistry of deuterated formic acid in a parahydrogen matrix

We report new FTIR studies of the 193 nm photochemistry of deuterated formic acid (DCOOD) trapped in parahydrogen matrices. In our 2011 preliminary report,\footnote{David T. Anderson, Leif O. Paulson, \textit{66th Ohio State University International Symposium on Molecular Spectroscopy}, talk FE02 (2011).} we showed the 193 nm \textit{in situ} photolysis of formic acid (HCOOH) produces small amounts of HCO and HOCO and that after the laser is turned off, we observe continued slow growth in the HOCO radical for up to 10 hours after photolysis. At that time we were unsure of the detailed chemical mechanism by which the HOCO continues to grow after photolysis, but we suspected it had to do with reactions of mobile H-atoms with the HCOOH precursor that remains at significant concentrations after photolysis under these conditions. The present deuterated formic acid photolysis studies provide strong circumstantial evidence that H-atom reactions with formic acid are the source of the continued HOCO growth. Further, variable-temperature kinetic studies conducted with the deuterated formic acid sample show a strong inverse temperature dependence to the reaction kinetics. Essentially, the reaction that leads to HOCO growth only occurs at temperatures below 2.4 K. We are currently trying to model the kinetics using standard methods and the most recent analysis will be presented at the meeting.Ope