IONIZATION ENERGIES, APPEARANCE ENERGIES, AND THERMOCHEMISTRY OF CF2OAND FCO

With the discharge flow-photoionization mass spectrometer (DF-PIMS) co upled to the U-11 beamline at the National Synchrotron Light Source, w e have measured the ionization energies of C2F4, CF2, and CF2O and app earance energy of FCO+ from CF2O. The PIMS results corroborate those d etermined by other techniques. With high-level ab initio calculations that utilize a large basis set and isogyric corrections, we have deter mined an ionization energy of 9.3 + 0.1 eV for FCO. At 298 K, the heat s of formation of FCO (-152 +/- 12 kJ/mol) and FCO+ (745.3 +/- 9.6 kJ/ mol) [relative to Delta(f)H(298)(0)(CF2O) = -607.9 +/- 7.1 kJ/mol] wer e determined and agree to within the uncertainties of other measuremen ts but with much higher precision. We have evaluated the bond strength s D-298(0)(F-CFO) and D-298(0)(F-CO) to be 535 +/- 12 anti 121 +/- 12 kJ/mol, respectively.