## 3 Results
### Temperature Profiles of Average Collision Cross Sections
Figure 8: Temperature dependence of the average electron–neutral collision cross sections of carbon dioxide (CO\({}_{2}\)), as obtained using four different methods. Figure 7: Temperature dependence of the average electron–neutral collision cross sections of carbon monoxide (CO), as obtained using four different methods. Figure 9 is used to contrast the four predicted curves of the average electron-neutral collision cross sections for nuclear vapor (H\({}_{2}\)O). All four methods agree about the decrease in \(\overline{Q}_{\rm H2O}\) as \(T_{e}\) increases (the opposite behavior to \(\overline{Q}_{\rm H2O}\)). Based on the arithmetic mean profile of the four individual profiles, the mean rate of change in \(\overline{Q}_{\rm H2O}\) is 0.0010537 A\({}^{2}\)/K. The predictions of methods 1 (\(\overline{u}_{e}=1.5\overline{T}_{e}\)) and 3 (integration) have similar values of \(\overline{Q}_{\rm H2}\), which together are noticeably larger than those predicted using methods 2 (linear) and 4 (quadratic). The distinction of the predictions into these two groups is the same situation observed for CO\({}_{2}\), but in the case of CO\({}_{2}\), the predictions of methods 1 and 3 are the lower-values group (not the higher-values group, as in the case of H\({}_{2}\)). Also, the gap between the two groups of predictions in the case of H\({}_{2}\) is not very large. For example, the ratio of the largest \(\overline{Q}_{\rm H2}\), obtained using method 3, to the smallest \(\overline{Q}_{\rm H2}\), obtained using method 2, is 1.3064 at 2000 K, and 1.2775 at 3000 K. The values of \(\overline{Q}_{\rm H2}\) are comparable to those of \(\overline{Q}_{\rm CO}\). As in the case of CO\({}_{2}\), the nonlinearity of \(\overline{Q}_{\rm H2}(T_{e})\) in methods 1 and 4 is not pronounced in the temperature range of interest here. This is similar to the case of CO\({}_{2}\), except that \(\overline{Q}_{\rm CO2}(T_{e})\) increases, not decreases, with (\(T_{e}\)). Figure 10 is used to contrast the four predicted curves of the average electron-neutral collision cross sections for water vapor (H\({}_{2}\)O). All four methods agree about the decrease in \(\overline{Q}_{\rm H2O}\) as \(T_{e}\) increases (the opposite behavior to \(\overline{Q}_{\rm H2}\)). Based on the arithmetic mean profile of the four individual profiles, the mean rate of change in \(\overline{Q}_{\rm H2O}\) is \(-0.0298717\) A\({}^{2}\)/K. The predictions of methods 1 (\(\overline{u}_{e}=1.5\overline{T}_{e}\)), 2 (linear), and 3 (integration) have similar values of \(\overline{Q}_{\rm H2O}\), which together are noticeably smaller than those predicted using method 4 (quadratic). The observation that one method of the four behaves very differently than the other three methods in terms of the values of \(\overline{Q}\) (but not in terms of its trend) was also found for CO, but in that case of CO, the outlier was method 3, not method 4. The values of \(\overline{Q}_{\rm H2O}\) are one order of magnitude larger than those of \(\overline{Q}_{\rm CO}\) and \(\overline{Q}_{\rm H2}\). This is an important feature of H\({}_{2}\)O, indicating that combustion plasma produced from burning hydrogen-rich fuels is expected to have a smaller plasma electric conductivity compared with combustion plasma produced from burning carbon-rich fuels, if all other conditions are the same and if  
Figure 9: Temperature dependence for the average electron–neutral collision cross sections of molecular hydrogen (H\({}_{2}\)), as obtained using four different methods. the additional effect of electron-ion and electron-electron scattering (Coulomb scattering) is equal. For example, when comparing the hot gaseous combustion products of hydrogen and the hot gaseous combustion products of carbon-rich coal, the former gases are expected to have a lower electric conductivity than the latter gases, assuming the same seeding amounts and same temperatures, as well as assuming the ions and electrons' effects on electron mobility are equal in both cases.