Exploration of vibrationally resolved threshold photoelectron spectrum of difluoromethane within photon energy range of 12.45–14.10 eV

Threshold photoelectron spectrum of CH2F2 in the photon energy range of 12.45–14.10 eV was re-investigated by means of a combination of photo-electron-photoion coincidence experiments and density functional theory calculations. A series of vibrational peaks were distinctly observed in this range. Using optimized geometries and vibrational frequencies of the CH2F2 neutral and its cation in ground state at the M06-2X/cc-pVTZ level of theory, Franck-Condon factor simulations were conducted. Taking into account anharmonicity influences, a perfect agreement between the simulated and experimental spectra has been achieved. From the reliable vibrational assignments, adiabatic and vertical ionization energies of CH2F2 are derived as 12.371 ± 0.010 eV and 13.281 ± 0.010 eV, respectively. In addition, the experimental frequencies of four vibrational modes with ai symmetry for CH2F2+(X2B1) ions are determined.