Vibrational assignments and energy analyses of 3,4-difluorophenylacetylene using resonance-enhanced multiphoton ionization and slow electron velocity-map imaging techniques

Here, we report spectroscopic investigations of 3,4-difluorophenylacetylene applying two-color resonant two-photon ionization (2C-R2PI) and slow electron velocity-map imaging (SEVI) techniques. With the assistance of density functional theory (DFT) calculations, vibrational modes of the S₀ neutral ground state, S₁ first electronic excited state, and D₀ cationic ground state were assigned. The adiabatic excitation energy of the S₁ ← S₀ electronic transition was determined to be 35639 ± 5 cm⁻¹ from the resonance-enhanced multiphoton ionization (REMPI) spectroscopy. Additionally, the adiabatic ionization potential was found to be 72398 ± 5 cm⁻¹ based on the SEVI spectra.