Electron transport, attachment and ionization in c-C4F8 and iso-C4F8

Simultaneous measurements of electron D /μ (diffusion coefficient/mobility) values, attachment and ionization coefficients are reported over the range 100< E / p <210 in perfluorocyclobutane (c-C 4 F 8 ) and the range 140< E / p <270 in perfluorobutene-2 (iso-C 4 F 8 ). Electron drift velocities have also been measured in these two isomers over the same range. The D /μ values in iso-C 4 F 8 are substantially lower than those in c-C 4 F 8 and indicate that the difference in the molecular structures of these two isomers is of profound importance in this context. In general, the D /μ values are significantly lower than those in the perfluoroalkanes C n F 2 n +2 ( n =1-4) or in SF 6 at comparable E / p values. Comparison of the attachment coefficients at any given D /μ in the range D /μ=1·6-3·2 V suggests that the (total) attachment cross section in c-C 4 F 8 is smaller than that in iso-C 4 F 8 . The drift velocities in iso-C 4 F 8 are consistently higher (by about 7·5%) than those in c-C 4 F 8 .