Mobilities of Negative Ions in SF6

摘要

Mass identified mobilities were measured at 300deg;K for negative ions formed by a pulsed spark discharge in SF6. Zero field mobilities of the four ion species, SF5minus;, SF6minus;, SF6minus;(SF6), and SF6minus;(SF6)2, were found to be 0.595thinsp;plusmn;thinsp;0.007, 0.542thinsp;plusmn;thinsp;0.007, 0.470thinsp;plusmn;thinsp;0.010, and 0.420thinsp;plusmn;thinsp;0.010 cm2Vminus;1middot;secminus;1, respectively. The SF6minus;(SF6)2ion was observed to be collisionally destroyed atEthinsp;sol;thinsp;nvalues greater than 100thinsp;times;thinsp;10minus;17Vmiddot;cm2. The present data indicate that the zero field mobility of 0.570 cm2Vminus;1middot;secminus;1previously reported by McAfee and Edelson and by McDaniel and McDowell may have referred to the unresolved SF5minus;1and SF6minus;ions. All four mobilities measured in this experiment are significantly below the predictions of the Langevin mobility theory in its polarization limit.