Study On Photoionization Of P-fluorophenlacetylene In The Excited State By Slow-electron Velocity-map Imaging

In this paper,the ground state,excited state,ionic ground state and photoionization dynamics of p-fluorophenlacetylene(p-FPA)were investigated by resonance-enhanced multiphoton ionization(REMPI)and slow electron velocity-mapping imaging(SEVI)in combination with the aid of density functional theory,infrared spectra and UV-Visible spectrum.The wavelength position of the first excited state was determined and the contributions of orbital transition by UV absorption spectrum and quantum chemistry calculation.The ground state vibrational structure was firstly assigned by IR spectrum.The REMPI spectrum in the S₁ state and SEVI spectrum in the D₀ state of p-FPA were obtained.According to the high-level quantum chemical calculation,the vibrational frequencies of S₁ state and D₀ state were assigned.Moreover,the adiabatic excitation energy and adiabatic ionization potential of p-FPA were determined 35622±5cm^-1 and70945±10cm^-1,respectively.The vibrational modes in the transitions of p-FPA were discussed by Franck-Condon simulation.The multimode mixing effect was clearly found at 200-600cm^-1and 1100-1400cm^-1 in the mode mixing of S₀-S₁.And the multimode mixing effect was obviously discovered at 500-700cm^-1 and 1200-1450cm^-1 in the mode mixing of S₁-D₀.Photoelectron angular distribution(PAD)of p-FPA near the ionization threshold was obtained by SEVI technique.The relationship was measured between the anisotropy parameters(?₂,?₄)of D₀0⁰ and photoelectron kinetic energy by angular distribution.