Ionization energy and active cation vibrations of trans-2-fluorostyrene

We applied the two-color resonant two-photon mass-analyzed threshold ionization (MATI) technique to record the cation spectra of trans-2-fluorostyrene by ionizing via six intermediate vibronic levels. The adiabatic ionization energy was determined to be 69 304 ± 5 cm⁻¹. The distinct MATI bands at 67, 124, 242, 355, 737, 806, 833, and 993 cm⁻¹ were assigned to the active cation vibrations related to out-of-plane substituent-sensitive bending vibrations and in-plane ring deformation and bending motions. Many combination vibrations were also observed. Our experimental results suggest that the molecular geometry and vibrational coordinates of the trans-2-fluorostyrene cation in the D₀ state resemble those of the neutral species in the S₁ state.