This paper deals with the measurement of the mobility of negative ions in the mixtures of ${\mathrm{CCl}}_4$ with Ar with the ${\mathrm{CCl}}_4$ ratio up to $33.3\%.$ The pulsed Townsend technique was employed to produce an integrated ionic avalanche 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 ${\mathrm{CCl}}_4^{-}.$ The $E/N$ range of measurement was 1–50 Td $\left(1\mathrm{}\mathrm{Td}{=10\mathrm{}}^{-17}{\mathrm{V}\mathrm{}\mathrm{cm}}^2\right).\mathrm{}$ Our measurements strongly suggest that attachment is the dominant process and only negative ions are formed.

• Received 13 November 2003

DOI:https://doi.org/10.1103/PhysRevE.69.046401