Pham Le Nhan, Nguyen Minh Tho
Department of Chemistry, KU Leuven , Celestijnenlaan 200F, B-3001 Leuven, Belgium.
Computational Chemistry Research Group, Ton Duc Thang University , Ho Chi Minh City, 778000 Vietnam.
J Phys Chem A. 2017 Mar 9;121(9):1940-1949. doi: 10.1021/acs.jpca.7b00245. Epub 2017 Feb 28.
Electronic structures of both the anionic and neutral triatomic species TiGe were theoretically studied employing single-reference (DFT and RCCSD(T)) and multiconfigurational (CASSCF/CASPT2 and CASSCF/NEVPT2) methods with large basis sets. The ground state of TiGe (C) was identified to be B, but the A state is nearly degenerate, whereas the B is clearly the ground state of the neutral TiGe (C). On the basis of the computed ground and excited states of both neutral and anionic structures, all electronic transitions giving rise to experimental anion photoelectron bands in the spectrum of TiGe can now be assigned. The X band of the anion photoelectron spectrum is attributed to a one-electron transition between two ground states B → B. Three neutral excited states 2A, 2B, and 3B are energetically responsible for the B band upon one-electron photodetachement from the anionic ground state B. The C band is assigned to the transition B → 2A. A transition from the nearly degenerate ground state A of the anion to the low-spin A of the final neutral state can be ascribed to the A band. Furthermore, the first two bands' progressions, whose normal vibrational modes were accessible from CASSCF/CASPT2 calculations, were also simulated by determination of multidimensional Franck-Condon factors.
采用单参考方法（DFT和RCCSD(T)）以及多组态方法（CASSCF/CASPT2和CASSCF/NEVPT2）并结合大基组，从理论上研究了阴离子和中性三原子物种TiGe的电子结构。已确定TiGe (C)的基态为B态，但A态几乎简并，而B态显然是中性TiGe (C)的基态。基于计算得到的中性和阴离子结构的基态及激发态，现在可以对TiGe光谱中产生实验阴离子光电子能带的所有电子跃迁进行归属。阴离子光电子能谱的X带归因于两个基态之间的单电子跃迁B→B。三个中性激发态2A、2B和3B在从阴离子基态B进行单电子光剥离时，对B带在能量上起作用。C带归属于跃迁B→2A。从阴离子的近简并基态A到最终中性态的低自旋A的跃迁可归因于A带。此外，通过确定多维弗兰克 - 康登因子，还模拟了前两个能带的进展情况，其正常振动模式可从CASSCF/CASPT2计算中获得。
