Negative ion formation and motion in a mixture of $CCl_{4}$ and $Ar$

This work deals with the measurement of the mobility of negative ions in the mixtures of $CCl_{4}$ with $Ar$ with the $CCl_{4}$ ratio up to $33.3\%$. The Pulsed Townsend Technique was employed to produce an integrated ionic avalanches over a range of the density-reduced electric field $E/N$ for which ionization is either negligible or absent, and attachment processes are dominant, leading to the formation of mostly $CCl_{4}^{-}$. The $E/N$ range of measurement was 1 to $50$ $Td$ (1$Td = 10^{-17} Vcm^{2})$ and gas pressure of $80 Torr$. Our measurements strongly suggest that attachment is the dominant process and only negative ions are formed. The characteristics of the measured transients, indicating that there is only one drifting ionic species. That, and the low $E/N$ values used, led to the assumption that the majority ion species under investigation is $CCl_{4}^{-}$. This method proved to be highly sensitive for detecting negative ion signals even for small amounts of $CCl_{4}$ in the mixture. The relevance of electron attachment processes in these gas mixtures are desirable and it is our hope that the present data are of use for gas discharge simulation and complex ion chemistry of $CCl_{4}/Ar$ mixtures.