NO+ formation pathways in dissociation of N2O+ ions at the C-2 Sigma(+) state revealed from threshold photoelectron-photoion coincidence velocity imaging

作者：Tang Xiaofeng; Niu Mingli; Zhou Xiaoguo^*; Liu Shilin; Liu Fuyi; Shan Xiaobin; Sheng Liusi

来源：Journal of Chemical Physics, 2011, 134(5): 054312.

DOI：10.1063/1.3549130

Using the novel threshold photoelectron-photoion coincidence (TPEPICO) velocity imaging technique, the dissociative photoionization of N2O molecule via the C-2 Sigma(+) ionic state has been investigated. Four fragment ions, NO+, N-2(+), O+, and N+, are observed, respectively, and the NO+ and N+ ions are always dominant in the whole excitation energy range of the C-2 Sigma(+) ionic state. Subsequently, the TPEPICO three-dimensional time-sliced velocity images of NO+ dissociated from the vibrational state-selected N2O+(C-2 Sigma(+)) ions have been recorded. Thus the kinetic and internal energy distributions of the NO+ fragments have been obtained directly as the bimodal distributions, suggesting that the NO+ fragments are formed via both NO+(X-1 Sigma(+)) + N(P-2) and NO+(X-1 Sigma(+)) + N(D-2) dissociation channels. Almost the same vibrational population reversions are identified for both dissociation pathways. Interestingly, the obtained branching ratios of the two channels exhibit some dependence on the excited vibrational mode for N2O+(C-2 Sigma(+)), in which the excited asymmetrical stretching potentially promotes dissociation possibility along the NO+(X-1 Sigma(+)) + N(D-2) pathway. In addition, the measured anisotropic parameters of NO+ are close to 0.5, indicating that the C-2 Sigma(+) state of N2O+ is fully predissociative, indeed, with a tendency of parallel dissociation, and therefore, the corresponding predissociation mechanisms for the N2O+(C-2 Sigma(+)) ions are depicted.

• 出版日期2011-2-7
• 单位中国科学技术大学