Electron motion in the gases ${\mathrm{CF}}_4$, ${\mathrm{C}}_2$${\mathrm{F}}_6$, ${\mathrm{C}}_3$${\mathrm{F}}_8$, and n-${\mathrm{C}}_4$${\mathrm{F}}_{10}$

The drift velocity w of electrons has been measured in the perfluoroalkanes n-${\mathrm{C}}_{\mathrm{N}}$ ${\mathrm{F}}_{2\mathrm{N}+2\mathrm{}}$ (N=1–4) over the density-reduced electric field (E/N) range 0.03×${10}^{\mathrm{-}17}$ V ${\mathrm{cm}}^2$≤E/N≤500×${10}^{\mathrm{-}17}$ V ${\mathrm{cm}}^2$ using a pulsed Townsend experimental method. The present measurements of w are the first to be obtained for ${\mathrm{C}}_2$ ${\mathrm{F}}_6$, ${\mathrm{C}}_3$ ${\mathrm{F}}_8$, and n-${\mathrm{C}}_4$ ${\mathrm{F}}_{10}$ at low E/N values. The electron-drift-velocity measurements in ${\mathrm{C}}_3$ ${\mathrm{F}}_8$ and n-${\mathrm{C}}_4$ ${\mathrm{F}}_{10}$ are dependent on gas pressure at high E/N values, even after allowing for nonequilibrium and boundary corrections to the measured electron swarm transit time. This is the first observation of a pressure dependence in the electron drift velocity in these gases and is believed to be due to changes in the electron energy distribution function f(ɛ,E/N) with gas pressure resulting from increases in the density-normalized electron attachment coefficient η/N with gas pressure. The perfluoroalkanes ${\mathrm{CF}}_4$, ${\mathrm{C}}_2$ ${\mathrm{F}}_6$, and ${\mathrm{C}}_3$ ${\mathrm{F}}_8$ exhibit regions of pronounced negative differential conductivity (NDC) similar to but smaller in magnitude than that in ${\mathrm{CH}}_4$. Possible mechanisms leading to the observation of NDC effects in these molecular gases are discussed.