Experimental and Theoretical Study on p-Chlorofluorobenzene in the S0, S1 and D₀ States

The geometric structures and vibration frequencies of para -chlorofluorobenzene ( p -ClFPh) in the first excited state of neutral and ground state of cation were investigated by resonance-enhanced multiphoton ionization and slow electron velocity-map imaging. The infrared spectrum of S _0 state and absorption spectrum for S _1 \leftarrow S _0 transition in p -ClFPh were also recorded. Based on the one-color resonant two-photon ionization spectrum and two-color resonant two-photon ionization spectrum, we obtained the adiabatic excited-state energy of p -ClFPh as 36302 \pm 4 cm ^-1 . In the two-color resonant two-photon ionization slow electron velocity-map imagin spectra, the accurate adiabatic ionization potential of p -ClFPh was extrapolated as 72937 \pm 8 cm ^-1 via threshold ionization measurement. In addition, Franck-Condon simulation was performed to help us confidently ascertain the main vibrational modes in the S _1 and D _0 states. Furthermore, the mixing of vibrational modes between S _0 \rightarrow S _1 and S _1 \rightarrow D _0 has been analyzed.