Production of OH from the collision-free photodissociation of nitromethane at 266 nm

Photodissociation of nitromethane, CH3NO2, at 266 nm under collision-free conditions results in the single photon production of electronic ground state OH(X 2Πi). A rotational ‘‘temperature’’ of 1750±50 K describes the rotational distribution of the nascent OH radical. A quantum yield of 0.004±0.001 is determined for the photolytic pathway producing the OH radical. Within experimental uncertainty, no Λ-doublet population preference was observed for OH production from H2O2, HNO3, or CH3NO2 photolysis. If a saturation correction is not utilized apparent Λ-doublet population differences are found. This incorrect saturation compensation may account for previous literature Λ-doublet population ratios, fi/ f′i, that are greater than one.