Photoionization of HOF with mass analysis

The ionization yields of HOF⁺, O⁺, and OH⁺ have been studied as a function of wavelength in the photoionization of HOF. The first ionization potential of HOF is 12.71±0.01 eV. The threshold for O⁺ formation, 14.34 eV, leads to $Δ Hf00 (HOF)=−22.8± 1 kcal/mole$⁠. The threshold for OH⁺ formation, 15.07 eV, leads to a value for $Δ Hf0 (HOF)$ in good agreement with the above result if one of two discrepant values for $Δ Hf0 (HO+)$ is chosen. This choice implies that the ionization potential for OH is 12.9_o±0.05 eV. The proton affinity of OF is 5.8₂ eV. Pronounced structure in the ionization yield curves is interpreted as vibrational autoionization in the region near threshold, and as electronic autoionization at higher photon energies.