Collisional cross sections of CCl2F2 and transport coefficients of CCl2F2 and N2-CCl2F2 mixtures

A set of effective electron collision cross sections, including momentum transfer, vibration, and electron excitation collisions has been determined for CCl2F2 gas: the momentum transfer is approximately 2×10−15 cm2 with the highest maximum about 4×10−15 at 6 eV, two vibrational maxima with thresholds of 0.11 and 0.14 eV are about 9 and 4 (10−16 cm2) at 0.2 and 0.25 eV and two excitation maxima with thresholds of 7.0 and 9.8 eV are 2.8 and 5.1 (10−16 cm2) at 11 and 18 eV, respectively. The calculated transport coefficients are in satisfactory agreement with measured values, except for the attachment coefficient, which is too high at low (below 90 V cm−1 Torr−1) and high (above 180 V cm−1 Torr−1) reduced fields. The possibility of comparison in the case of N2-CCl2F2 mixtures is limited and agreement is less satisfactory than in the case of pure CCl2F2. Deviations for medium fields are within about 30% for the D/μ ratio and ionization coefficients. The attachment coefficients agree well at high partial density of CCl2F2 (above approximately 50%) but the experimental values are much higher than predicted at low CCl2F2 content. Calculated values of the limit fields agree well with the values obtained from breakdown potential measurements available in the literature.