Experimental absolute electron impact ionization cross-sections of Cl2

We measured absolute partial cross-sections for the formation of Cl2+, Cl22+, Cl+ and Cl2+ ions following electron impact on molecular chlorine (Cl2) from threshold to 900 eV using a time-of-flight mass spectrometer. The ion spectrum at all impact energies is dominated by the singly charged ions with maximum cross-section values of 4.6 × 10−16 cm2 for Cl2+ at 32 eV and 4.0 × 10−16 cm2 for Cl+ at 70 eV. The cross-sections for the formation of the doubly charged ions are more than one order of magnitude lower. Double ionization processes account for about 6% of the total ion yield at 70 eV. The absolute total ionization cross-section of Cl2 was obtained as the sum of all measured partial ionization cross-sections. To the extent possible, a comparison of our results with other available measured and calculated data is made.