# Electron Impact Cross Sections and Transport Studies of C\({}_{3}\)F\({}_{6}\)[PERSON]
## 1 Introduction  
In recent years, we have been looking for stable gases with good insulating and breakdown characteristics in light of the replacement of SF\({}_{6}\) in various plasma applications [1; 2; 3]. SF\({}_{6}\), as a strong greenhouse gas, represents a significant environmental threat. It also produces some toxic products as a consequence of its decomposition [3]. Thus, we aimed to identify an environmentally friendly gas with a better, or at least similar, insulation performance as that of SF\({}_{6}\). The evaluation indices of alternative gases that indicate good properties are a high breakdown voltage, a high critical field strength, a positive synergistic effect, a low electron drift velocity, a low diffusion coefficient, a low ionization coefficient, and a high attachment coefficient. Further, the toxicity of decomposition products should also be low as should the low global warming potential (GWP). In our recent work [4], we conducted a quantum chemistry study on perfluoro-methyl-vinyl-ether (PMVE), C\({}_{3}\)F\({}_{6}\)O, with a GWP of 0.004 [5], see Figure 1. The ionization energy, electron affinity, and band gap suggest that the gas has good electron-absorbing properties and is chemically stable. Further, most of the decomposition and recombination productsare nontoxic. Encouraged by the results, we analyzed the electron transport properties of PMVE. Our main aim was to estimate the Townsend coefficients to obtain the dielectric strength of the pure gas. Moreover, it is known that gas mixtures can be used to minimize the negative environmental impact and maximize the dielectric strength. The liquefaction temperature of PMVE is \(-22\)\({}^{\circ}\)C [6]. If a lesser liquefaction temperature is needed, the pure gas must be mixed with buffer gases. We selected the most commonly used buffer gases--CO\({}_{2}\), O\({}_{2}\), and N\({}_{2}\)--for our analysis. Finding the optimal mixture ratio for the buffer gas is also very important. For the dielectric strength of a gas mixture, the synergistic effect [7] is usually used to evaluate and optimize the choice of gases in the mixture and the mixed ratio. The determination of Townsend coefficients, dielectric strengths, and the study of synergistic effect requires a transport study. For this task, we solved the electron Boltzmann equation using two-term approximation using BOISIG+ [8]. Further, this method does not directly give the breakdown voltage. We performed a fitting of the ionization coefficients to plot the breakdown voltage curve and estimate the minimum breakdown voltage [9; 10]. As mentioned earlier, any replacement gas should have a higher dielectric strength and breakdown voltage. Buffer gases can again be of great help to obtain an optimal value of both these important properties. At the heart of transport studies lies the accurate determination of scattering cross sections. In the literature, we found only one recent article dedicated to the cross section measurement of PMVE in the intermediate energy range [11]. The authors report the total scattering cross section in the energy range 15-90 eV. However, we needed a complete cross section set for electron-PMVE scattering. Owing to the lack of such studies in the past, we computed the cross sections using the Quantemol-EC (QEC) software [12]. QEC is based on the well-known R-matrix method [13]. R-matrix provides a reliable dataset in the low-energy region. We obtained elastic, momentum transfer, electronic excitation, rotational excitation, and attachment cross sections. These low-energy cross sections were linearly extrapolated to higher energies using the transport codes. For the ionization cross section, we used the binary-encounter-Bethe (BEB) method [14], which extends from the low to high energy range. This work is the first report of the low-energy cross section and transport parameters of PMVE. The cross sections are reported for an energy range of 1-15 eV and the transport study was performed over the density-normalized electric field strength E/N, between 100 and 1000 Td.