Department of Chemistry, Technical University of Munich, Lichtenbergstr. 4, 85747 Garching, Germany.
J Chem Phys. 2012 Jul 14;137(2):021101. doi: 10.1063/1.4732054.
UV absorption cross section of CO(2) is studied using high level ab initio quantum chemistry for electrons and iterative quantum dynamics for nuclear motion on interacting global full dimensional potential energy surfaces. Six electronic states-1, 2, 3(1)A(') and 1, 2, 3(1)A(")-are considered. At linearity, they correspond to the ground electronic state X̃(1)Σ(g) (+) and the optically forbidden but vibronically allowed valence states 1(1)Δ(u), 1(1)Σ(u) (-), and 1(1)Π(g). In the Franck-Condon region, these states interact via Renner-Teller and conical intersections and are simultaneously involved in an intricate network of non-adiabatic couplings. The absorption spectrum, calculated for many rotational states, reproduces the distinct two-band shape of the experimental spectrum measured at 190 K and the characteristic patterns of the diffuse structures in each band. Quantum dynamics unravel the relative importance of different vibronic mechanisms, while metastable resonance states, underlying the diffuse structures, provide dynamically based vibronic assignments of individual lines.
使用高精度的电子从头计算量子化学和核运动的迭代量子动力学，研究了 CO(2) 的紫外吸收截面。考虑了六个电子态-1、2、3(1)A(') 和 1、2、3(1)A(")-。在线性情况下，它们对应于基态电子态 X̃(1)Σ(g) (+)和光学禁阻但振动允许的价态 1(1)Δ(u)、1(1)Σ(u) (-)和 1(1)Π(g)。在 Franck-Condon 区域，这些态通过 Renner-Teller 和锥形交叉相互作用，并同时参与到复杂的非绝热耦合网络中。计算了许多转动态的吸收光谱，重现了在 190 K 测量的实验光谱的独特双峰形状以及每个带中的漫射结构的特征图案。量子动力学揭示了不同振动态机制的相对重要性，而潜在的漫射结构的亚稳态共振态为各条线提供了基于动力学的振动态分配。
