Threshold Ionization of HCl by Electron Impact

Abstract

The ionization of HCl by electron impact is studied in a mass spectrometer with a pseudomonoenergetic electron beam. The ionization potential of HCl is determined as 12.56±0.1 ev. The ionization curve at threshold exhibits excessive curvature which is attributed to the ²Π_i doublet ground states of the ion estimated to be separated by 0.3 ev. A sharp change in slope of the ionization curve at 1.6 ev above threshold is attributed to the onset of ionization of the A²Σ⁺ excited state of HCl⁺.