Mobility of daughter negative ions in iodo-fluorocarbon, fluorocarbon, and hydrofluorocarbon parent gases

摘要

We have measured the mobility of positive ions in C_(2)F_(4) and C_(4)F_(8), and that for negative ions in C_(2)F_(6), CHF_(3), CF_(3)I and its mixtures with N_(2), Ar and Xe from a discharge in the Townsend regime. These measurements were performed over a range of the density-normalized electric field of 4-600X10~(-17) V cm~(2). Mostly based on previous ion beam experiments, we have identified the predominant drifting ion in the discharge is C_(2)F_(4)~(+) for C_(2)F_(4) and c-C_(4)F_(8), F~(-) for C_(2)F_(6) and CHF_(3), and I~(-) for CF_(3)I. By considering the influence of a permanent dipole moment (CHF_(3) and CF_(3)I), we have obtained a better agreement between the low-field measured and calculated mobilities, as compared to those calculated from Langevin's polarisation-limit formula. The mobility of negative ions in CF_(3)I-N_(2), CF_(3)I-Ar and CF_(3)I-Xe mixtures agrees reasonably well with the predicted values by standard Blanc's law.