Beyond Born-Oppenheimer based diabatic surfaces of 1,3,5-CHF 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-CHF over a series [eighteen (18)] of two-dimensional (2D) nuclear planes constituted with eleven normal modes (, , , , , , , , , and ) to include all possible nonadiabatic interactions among six coupled electronic states (X̃E'', , B̃E' and ). We had formulated explicit expressions of adiabatic to diabatic transformation (ADT) equations [S. Mukherjee, J. Dutta, B. Mukherjee, S. Sardar and S. Adhikari, , 2019, , 064308] for the same system forming six state sub-Hilbert space and at present, these ADT equations are solved by incorporating MRCI level 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-CHF. Our theoretically calculated spectra for X̃E'', 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.