Experimental absolute electron impact ionization cross-sections of Cl ₂

We measured absolute partial cross-sections for the formation of Cl ₂⁺, Cl₂²⁺, Cl⁺ and Cl²⁺ ions following electron impact on molecular chlorine (Cl ₂) 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 cm ² 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 Cl ₂ 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.