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Journal of Physical Chemistry A, Vol.113, No.14, 3303-3310, 2009
Photodissociation Dynamics of Alkyl Nitrites at 266 and 355 nm: The OH Product Channel
Photodissociation of methyl nitrite and n-butyl nitrite at 266 and 355 nm has been investigated in the gas phase at room temperature. OH photoproducts were observed, and their internal state distributions were measured by the one-photon laser-induced fluorescence (LIF) technique. It was found that the nascent OH from the 266 nm photolysis of methyl nitrite was vibrationally cold, and its rotational state distribution conformed to a Boltzmann behavior with a rotational temperature of T-rot = 2200 +/- 150 K. In contrast, the nascent OH from the 266 nm photolysis of n-butyl nitrite was found to be vibrationally excited, and the measured relative population of upsilon '' = 0: 1 was 0.78: 0.22. The rotational state distribution of the OH upsilon '' = 1 state conformed to Boltzmann behavior, with a rotational temperature of T-rot = 1462 +/- 120 K. However, a simple Boltzmann distribution was not found for the OH upsilon '' = 0 state. In the photolysis of n-butyl nitrite at 355 nm, the OH fragment was found to be vibrationally cold and its rotational state distribution showed non-Boltzmann behavior. A photodissociation mechanism involving an intramolecular hydrogen atom transfer process is proposed for the OH product pathway for methyl nitrite, which has been compared with the potential energy surfaces obtained from density functional theory (DFT) calculations. A photodissociation mechanism of n-butyl nitrite is also proposed for the OH product pathway, which differs from that of methyl nitrite due to the effects of the different alkoxy substituents.