Photodissociation Dynamics of Nitromethane and Nitroethane at 266 nm

Abstract

Measurements of the nascent OH product from photodissociation of gaseous nitromethane and nitroethane at 266 nm were performed using the single-photon laser induced fluorescence technique. The OH fragment is found to be vibrationally cold for both systems. The rotational state distribution of nitromethane are Boltzmann, with rotational temperature of Trot=2045150 and 1923150 K for both 23/2 and 21/2 states, respectively. For nitroethane, the rotational state distribution shows none Boltzmann and cannot be well characterized by a rotational temperature, which indicates the different mechanisms in producing OH radicals from photodissociation of nitromethane and nitroethane. The rotational energy is calculated as 14.360.8 and 4.980.8 kJ/mol for nitromethane and nitroethane, respectively. A preferential population of the low spin-orbit component (23/2) is observed for both nitromethane and nitroethane. The dominant population of + state in two -doublet states is also observed for both nitromethane and nitroethane, which indicates that the unpaired lobe of the OH fragment is parallel to the plane of rotation.