Max-Planck-Institut für Dynamik und Selbstorganisation, D-37073 Göttingen, Germany.
J Chem Phys. 2011 Feb 14;134(6):064313. doi: 10.1063/1.3553377.
The ultraviolet photodissociation of N(2)O is studied by wave packet calculations using global three-dimensional potential energy surfaces for the two lowest (1)A' states. The incorporation of all internal degrees of freedom in the dynamics calculations is essential for a realistic treatment. The room-temperature absorption cross section is well reproduced, including the weak vibrational structures. Classical periodic orbits show that the latter can be attributed to large-amplitude NN stretch motion combined with strong excitation of the bend. Weakening of the NN bond toward the N + NO channel is the necessary prerequisite. The temperature dependence of the calculated cross section is significant, as expected for a dipole-forbidden transition of a linear molecule; but it is not as strong as observed experimentally [G. S. Selwyn and H. S. Johnston, J. Chem. Phys. 74, 3791 (1981)]. This shortcoming is due to an apparent underestimation of the (0,1,0) hot band absorption. On the other hand, the calculations yield reasonable predictions of the ratios of bending-state resolved absorption cross sections, σ(0, 1, 0)∕σ(0, 0, 0) and σ(0, 2, 0)∕σ(0, 0, 0), measured at 204 nm [H. Kawamata et al. J. Chem. Phys. 125, 133312 (2006)].
利用全局三维势能面，通过波包计算研究了 N(2)O 的紫外光解。在动力学计算中纳入所有内部自由度对于真实处理至关重要。室温吸收截面得到了很好的再现，包括弱振动结构。经典的周期轨道表明，后者可以归因于大振幅 NN 拉伸运动与强烈激发弯曲运动的结合。向 N + NO 通道削弱 NN 键是必要的前提条件。与线性分子的偶极禁止跃迁一致，计算截面的温度依赖性非常显著；但与实验观察到的情况相比并不强烈[G. S. Selwyn 和 H. S. Johnston，J. Chem. Phys. 74, 3791（1981）]。这种缺陷是由于对（0,1,0）热带吸收的明显低估。另一方面，计算结果合理地预测了在 204nm 处测量的弯曲态分辨吸收截面比，σ(0, 1, 0)∕σ(0, 0, 0)和 σ(0, 2, 0)∕σ(0, 0, 0)[H. Kawamata 等人，J. Chem. Phys. 125, 133312（2006）]。
