Beyond Born-Oppenheimer based diabatic surfaces of 1,3,5-C 6 H 3 F 3 + to generate the photoelectron spectra using time-dependent discrete variable representation approach.

In this article, Beyond Born-Oppenheimer (BBO) treatment is implemented to construct diabatic potential energy surfaces (PESs) of 1,3,5-C ₆ H ₃ F ₃ ⁺ over a series [eighteen (18)] of two-dimensional (2D) nuclear planes constituted with eleven normal modes ( Q ₂ , Q _{9 x} , Q _{9 y} , Q _{13 x} , Q _{13 y} , Q _{18 x} , Q _{18 y} , Q _{10 x} , Q _{10 y} , Q _{12 x} and Q _{12 y} ) to include all possible nonadiabatic interactions among six coupled electronic states (X̃ ² E'', , B̃ ² E' and ). We had formulated explicit expressions of adiabatic to diabatic transformation (ADT) equations [S. Mukherjee, J. Dutta, B. Mukherjee, S. Sardar and S. Adhikari, J. Chem. Phys. , 2019, 150 , 064308] for the same system forming six state sub-Hilbert space and at present, these ADT equations are solved by incorporating MRCI level ab initio adiabatic PESs and CP-MCSCF calculated nonadiabatic coupling terms (NACTs) to derive diabatic PESs and couplings. Such single-valued, smooth, symmetric and continuous diabatic surface matrices are utilized to carry out multi-state multi-mode nuclear dynamics with the help of time-dependent discrete variable representation (TDDVR) methodology to compute the photoelectron (PE) spectra of 1,3,5-C ₆ H ₃ F ₃ . Our theoretically calculated spectra for X̃ ² E'', and states using BBO treatment and TDDVR dynamics show peak by peak correspondence with the experimental results as well as better than the findings of the multi-configuration time-dependent Hartree (MCTDH) method.