A method is presented for measuring appearance potentials with an analytical mass spectrometer. Slight modifications of the ion source and a unique method of interpreting ionization efficiency curves produce values which are generally accurate to within 0.5 per cent. Electron energy in the bombarding beam is partially controlled by a grid. The differential ion current due to a small change in ionizing potential is recorded and the interpretation produces efficiency curves which approach the form which could be obtained with mono-energetic electrons. Conventional use of the instrument is not affected by the modification. Bond-strengths determined from data by this method are in good agreement with published data.
W. J. Lambdin, B. L. Tuffly, and V. A. Yarborough, "Appearance Potentials as Obtained with an Analytical Mass Spectrometer," Appl. Spectrosc. 13, 71-74 (1959)