Mass Spectrometric Determination of Appearance Energies for Ions Formed from CoF4 and CoF3 molecules.

Knudsen cell mass spectrometry was applied to the evaluation of the ionization efficiency curves for the ions originating from CoF4 molecules. Cobalt tetrafluoride was obtained in the gas phase over the CoF3(s)- TbF4(s) system in the temperature range from 640 to 690 K. From the ionization efficiency curves the appearance energies of the ions formed from the CoF4 molecules were determined by means of Vogt's deconvolution method. Clausius-Clapeyron plots for the ions from CoF4 molecules were measured. Evaporation of pure CoF3(s) was carried out, and the appearance energies of the ions formed from CoF3 molecules were determined. The ionization energies for CoF4 and CoF3 molecules were found to be (14.3 0.2) and (13.3 0.1) eV, respectively.