Collisional cross sections of c-C4F8 and transport coefficients of c-C4F8 and N2-c-C4F8 mixtures

An effective set of collisional cross sections of c-C4F8 was determined by fitting the transport coefficients, i.e., drift velocity, diffusion, ionization, and attachment coefficients, to available experimental data. The best fit was obtained for the following values: a total momentum transfer cross section of 8×10−15 cm2 for electron energies of z≤4 eV dropping to 1.75×10−15 cm2 for z>12 eV, a maximum vibrational cross section of 8×10−15 cm2 at 0.4 eV, and an excitation cross section of about 4×10−16 cm2 between 9 and 20 eV. Ionization and attachment cross sections based on measurements by M. V. Kurepa [Transactions of the 3rd Czechoslovak Conference on Electronics and Vacuum Physics (Academia, Prague, 1967), p. 107] were used; the ionization cross section was multiplied by a correction factor of 0.59, while the attachment cross sections were readjusted according to measurements by C. Lifshitz and R. Grajower [Int. J. Mass Spectrom. Ion Phys. 10, 25 (1972/73)] and I. Sauers, L. G. Christophorou, and J. G. Carter [J. Chem. Phys. 71, 3016 (1979)]. Calculations of the transport coefficients of N2-c-C4F8 mixtures were also performed.