Motion of SF_x⁺ (x=1–3,5) and ion conversion in SF₆-N₂ mixtures

This paper reports on the mass-analyzed measurement of the drift velocity of the positive SF₆ daughter ions, SF_x⁺ (x=1–3,5) in the mixture of SF₆ with N₂ for SF₆ concentrations of 10% and 50%. A double mass spectrometer-drift tube was used for these measurements. The density-normalized electric field intensity E/N, was varied from 30 to 360 Td (1 Td=10^-17 Vcm²). We have found an increasingly monotonic dependence of the drift velocity with E/N, and an inverse dependence of the above parameter with the decrease of the SF₆ content in the mixture. A test of Blanc’s law for the zero-field reduced mobilities of the above ions shows a fair qualitative agreement. No drift velocities of these ionic species could be measured in pure N₂, since we found that these ions reacted strongly with the nitrogen molecules. The cases for SF₃⁺ and SF₅⁺ are discussed. A similar behavior was observed for the nitrogen ions drifting in pure SF₆.