Vibrational state distribution of highly vibrationally excited NO(X 2Π) generated from the reaction of O(1D) with N2O

Abstract

The vibrational state distribution has been determined for vibrationally excited NO(X ²Π; v = 11–17) produced by the reaction of O(¹D) with N₂O. O(¹D) atoms were generated by O₃ photodissociation at 266 nm and the laser-induced fluorescence (LIF) technique via the NO B ²Π←X ²Π transition was utilized to obtain the vibrational state distribution. The LIF spectra were taken under conditions in which the vibrational relaxation of NO is negligible while its rotational relaxation is sufficiently achieved. The rate constant for quenching by O₃ was also determined, as the loss of NO(B) due to quenching by reactant gases should be taken into account when the LIF data are analysed. Based on the large exothermicity of this reaction, significant excitation in the vibrational state of NO(X) is expected; however, the vibrational state distribution was similar to, but slightly colder than, that predicted from statistical theories. Possible mechanisms which may explain such an unexpected distribution are discussed.