Measurements of absolute total and partial cross sections for the electron ionization of tungsten hexafluoride (WF₆)

We measured absolute partial cross sections for the formation of positive ions followed by electron impact on tungsten hexafluoride (WF₆) from threshold to 900 eV using a time-of-flight mass spectrometer (TOF-MS). Dissociative ionization processes resulting in seven different singly charged ions (F⁺, W⁺, WF_x⁺, x=1-5) and five doubly charged ions (W²⁺, WF_x²⁺, x=1-4) were found to be the dominant ionization channels. The ion spectrum at all impact energies is dominated by WF₅⁺ fragment ions. At 120 eV impact energy, the partial WF₅⁺ ionization cross section has a maximum value of 3.92×10^-16 cm² that corresponds to 43% of the total ion yield. The cross section values of all the other singly charged fragment ions at 120 eV range between 0.39×10 ^-16 and 0.73×10^-16 cm². The ionization cross sections of the doubly charged ions are more than one order of magnitude lower than the cross section of WF₅⁺. Double ionization processes account for 21% of the total ion yield at 120 eV. The absolute total ionization cross section of WF₆ was obtained as the sum of all measured partial ionization cross sections and is compared with available calculated cross sections.