A discharge flow-photoionization mass spectrometric study of the FO(X 2Π i) radical : Photoionization efficiency spectrum and ionization energy

Abstract

Photoionization efficiency spectra of FO were measured over the wavelength range 80.0–100.0 nm and in the ionization threshold region, 94.0–100.0 nm, using a discharge flow-photoionization mass spectrometer apparatus coupled to a synchrotron radiation source, FO was generated by the reaction of F( 2P) atoms with NO 3 and via a F 2/O 2 discharge. A value of 12.78 ± 0.03 eV was obtained for the adiabatic ionization energy of FO from photoion thresholds which corresponds to FO + (X 3∑ −) ← FO(X 2Π i ). These results, which are the first to be obtained by direct PIMS measurements, corroborate those of a photoelectron spectroscopy study; however, the ionization energy determined here is free from interferences due to other species which complicated the PES measurement. A value of 109.5 ± 8.0 kJ mol −1 for Δ f H 0 298(FO) is computed from the present value of IE(FO) and a previous appearance energy measurement, and a value for the proton affinity of FO is calculated to be 511.5 ± 10.0 kJ mol −1.