A DISCHARGE FLOW-PHOTOIONIZATION MASS-SPECTROMETRIC STUDY OF THE FO(X(2)PI(I)) RADICAL - PHOTOIONIZATION EFFICIENCY SPECTRUM AND IONIZATION-ENERGY

Photoionization efficiency spectra of FO were measured over the wavele ngth range 80.0-100.0 nm and in the ionization threshold region, 94.0- 100.0 nm, using a discharge flow-photoionization mass spectrometer app aratus coupled to a synchrotron radiation source. FO was generated by the reaction of F(P-2) atoms with NO3 and via a F-2/O-2 discharge. A v alue of 12.78 +/- 0.03 eV was obtained for the adiabatic ionization en ergy of FO from photoion thresholds which corresponds to FO+(X(3) Sigm a(-))<-- FO(X(2) Pi(i)). These results, which are the first to be obta ined 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 PE S measurement. A value of 109.5 +/- 8.0 kJ mol(-1) for Delta(f)H(298)( 0) (FO) is computed from the present value of IE(FO) and a previous ap pearance energy measurement, and a value for the proton affinity of FO is calculated to be 511.5 +/- 10.0 kJ mol(-1)