Unimolecular dissociation is an important loss mechanism for atmospheric hydroperoxides (R-O-OH) leading to the production of OH radicals via the rupture of the weak O-O bond. Here we present results from the unimolecular dissociation of peroxyformic acid (PFA) initiated by exciting the molecule in the vicinity of its fifth OH stretching overtone state (6νOH) at both 615 and 626nm. Based on the estimated heat of formation of PFA and its fragments, the O-O bond dissociation energy (D0) in PFA is estimated to be ~45.1 kcal/mol. Thus, exciting room temperature PFA molecules at 615 nm and 626 nm is expected to leave the OH + HCO2 fragments with roughly 3.3 kcal/mol and 2.5 kcal/mol of available energy, respectively. Using laser induced fluorescence (LIF), we have probed the OH fragments from the near threshold unimolecular dissociation and have determined the partitioning of the available energy in to its internal and translational degrees of freedom. The internal energy of the OH fragments are also compared with predictions of phase space theory. These results, along with the insight they provide regarding the unimolecular dissociation dynamics of HC(O)OOH, will be presented.

Near threshold unimolecular dissociation of peroxyformic acid initiated through vibrational overtone excitation to the 6νOH state

ACS Spring 2022

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