The photofragmentation of methyl hydroperoxide CH 3OOH at 193 and 248 nm in a cold molecular beam

Abstract

The photodissociation of methyl hydroperoxide (CH 3OOH) has been studied in a molecular beam by photofragment translational spectroscopy. As CH 3OOH rapidly decomposes upon contact with metal, a new metal-free molecular beam source was designed, which is also suited to the generation of beam pulses of corrosive gases. After excitation at 193 and 248 nm, CH 3OOH decays exclusively into CH 3O+OH. At 193 nm, the average kinetic energy of the fragments 〈 E t〉=67 kcal/mol, corresponding to ≈ 65% of the available energy and implying an average internal energy 〈 E int〉=37kcal/mol. A very similar partitioning was observed at 248 nm with 〈 E t〉=48 kcal/mol (≈67%) and 〈 E int>=23 kcal/mol. According to these data, the secondary decay CH 3O→CH 2O+H is expected to be efficient (≈50%) only for λ exc=193 nm.