Titanium Digermanium: Theoretical Assignment of Electronic Transitions Underlying Its Anion Photoelectron Spectrum.
Le Nhan PhamMinh Tho NguyenPublished in: The journal of physical chemistry. A (2017)
Electronic structures of both the anionic and neutral triatomic species TiGe2-/0 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 TiGe2- (C2v) was identified to be 4B1, but the 2A1 state is nearly degenerate, whereas the 3B1 is clearly the ground state of the neutral TiGe2 (C2v). 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 TiGe2- can now be assigned. The X band of the anion photoelectron spectrum is attributed to a one-electron transition between two ground states 4B1 → 3B1. Three neutral excited states 23A2, 25B1, and 35B1 are energetically responsible for the B band upon one-electron photodetachement from the anionic ground state 4B1. The C band is assigned to the transition 4B1 → 25A1. A transition from the nearly degenerate ground state 2A1 of the anion to the low-spin 1A1 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.