Active vibrations of 1-cyanonaphthalene cation studied by mass-analyzed threshold ionization spectroscopy

We apply the two-color resonant two-photon mass-analyzed threshold ionization (MATI) spectroscopic technique to record the cation spectra of 1-cyanonaphthalene via four intermediate vibronic levels. The adiabatic ionization energy is determined to be 69 466 ± 5 cm−1. The distinct bands at 416, 472, 516, 669, and 852 cm−1 result from in-plane ring deformation vibrations of the cation. Analysis of these MATI spectra suggests that the molecular geometry and vibrational coordinates of the observed vibrations of the cation in the ground D0 state resemble those of the neutral in the electronically excited S1 state.