Theoretical Elucidation of Photoelectron Spectrum of Diphosphatriazolate Anion, P₂N₃

In this study, the 193 nm photoelectron spectrum of P₂$N_3^{-}$ is analyzed using comprehensive ab initio electronic structure and quantum dynamics computations, with a focus on the first five low-lying electronic states ($\tilde{X}$, Ã, B̃, C̃, and D̃) of P₂N₃. A 5 × 5 model Hamiltonian is constructed within a diabatic electronic framework to facilitate time-dependent (TD) and time-independent (TI) quantum chemical calculations. Nonadiabatic effects arise from energetically close electronic states possessing multiple crossings and conical intersections within them. The experimental photoelectron spectrum is thoroughly interpreted, accounting for all of the observed peaks and proper vibronic assignments. Notably, the first peak corresponds to four electronic states $\tilde{X}$, Ã, B̃ and C̃, while the second peak is attributed to the D̃ state of P₂N₃. Overall, our theoretical model deduced spectra coincide satisfactorily with the experimental results.