Vibronic and cation spectroscopy of p-ethynylaniline

We applied the resonant two-photon ionization and mass-analyzed threshold ionization spectroscopic techniques to record the vibronic and cation spectra of p-ethynylaniline. The cation spectra were obtained by ionizing via the 00, 121, and 11 levels of the electronically excited S1 state. The band origin of the S1 ← S0 electronic excitation and the adiabatic ionization energy were found to be 32 656 ± 2 cm−1 and 61 270 ± 5 cm−1, respectively. The observed active modes result from the in-plane ring deformation, substituent-sensitive in-plane bending, and out-of-plane vibrations.