## 3 Results and Discussion
### Experimental Results
#### 3.1.2 Optical Emission Spectroscopy
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Species** & \(\mathbf{\lambda}\) **(nm)** & **Transition Name** & **Transition Symbol** & \(\mathbf{v}^{{}^{\prime}}\) & \(\mathbf{v}^{{}^{\prime}}\) \\ \hline OH(Q) & 306–312 & Molecular Transition & \(A^{2}\Sigma\to X^{2}\Pi\) & 0 & 0 \\ \hline \multirow{4}{*}{\(CO_{2}\)} & \multirow{2}{*}{326.1} & Fox, Duffendack and Barker’s System & \(X^{2}\Pi_{g}\to A^{2}\Pi_{u}\) & 3 & 1a \\ \cline{2-6}  & & & & & \\ \cline{2-6}  & \multirow{2}{*}{338.3} & Fox, Duffendack and Barker’s System & \(X^{2}\Pi_{g}\to A^{2}\Pi_{u}\) & 2 & 0 \\ \cline{2-6}  & & & & & \\ \cline{2-6}  & \multirow{2}{*}{368.2} & Fox, Duffendack and Barker’s System & \(X^{2}\Pi_{g}\to A^{2}\Pi_{u}\) & 1 & 2 \\ \hline \multirow{4}{*}{\(CO_{2}^{+}\)} & \multirow{2}{*}{387.5} & Fox, Duffendack and Barker’s System & \(X^{2}\Pi_{g}\to A^{2}\Pi_{u}\) & 2 & 4 \\ \cline{2-6}  & & & & & \\ \cline{2-6}  & \multirow{2}{*}{407.3} & Fox, Duffendack and Barker’s System & \(X^{2}\Pi_{g}\to A^{2}\Pi_{u}\) & 1 & 4 \\ \hline \multirow{2}{*}{H} & \multirow{2}{*}{486.1} & H\({}_{\beta}\) Balmer series line & n = 4 \(\rightarrow\) n = 2 & - & - \\ \cline{2-6}  & 656.3 & H\({}_{\alpha}\) Balmer series line & n = 3 \(\rightarrow\) n = 2 & - & - \\ \hline \multirow{4}{*}{\(C_{2}\)} & 471.6 & Swan System & \(A^{3}\Pi_{g}\to B^{3}\Pi_{u}\) & 0 & 1 \\ \cline{2-6}  & 516.4 & Swan System & \(A^{3}\Pi_{g}\to B^{3}\Pi_{u}\) & 0 & 0 \\ \cline{2-6}  & 560.1 & Swan System & \(A^{3}\Pi_{g}\to B^{3}\Pi_{u}\) & 1 & 0 \\ \hline \multirow{4}{*}{\(CO\)} & 589.5 & High Pressure Bands & \(A^{3}\Pi_{g}\to B^{3}\Pi_{u}\) & 6 & 8 \\ \cline{2-6}  & 458.5 & The Triplet Bands & \(d^{3}\Pi\to a^{3}\Pi\) & 6 & 0 \\ \cline{2-6}  & 564.2 & The Triplet Bands & \(d^{3}\Pi\to a^{3}\Pi\) & 2 & 0 \\ \cline{2-6}  & 601.4 & The Triplet Bands & \(d^{3}\Pi\to a^{3}\Pi\) & 1 & 0 \\ \cline{2-6}  & 643.2 & The Triplet Bands & \(d^{3}\Pi\to a^{3}\Pi\) & 0 & 0 \\ \hline \multirow{4}{*}{\(CO^{+}\)} & \multirow{2}{*}{427.3} & Comet-tail system & \multirow{4}{*}{\(X^{2}\Pi\to A^{2}\Sigma\)} & \multirow{2}{*}{2} & 0 \\  & & & & & \\ \cline{2-6}  & \multirow{2}{*}{385.3} & Chamberlains Airglow System & & & \\ \cline{2-6}  & & & & & \\ \hline \multirow{2}{*}{\(O_{2}^{+}\)} & \multirow{2}{*}{550–600} & Molecular emission Band & & & \\ \cline{2-6}  & & & & & \\ \hline \multirow{2}{*}{O} & 777.1 & Atomic Transition & 3p\({}^{5}\)P \(\rightarrow\) 3s\({}^{5}\)S & - & - \\ \cline{2-6}  & 843.2 & Atomic Transition & 3p\({}^{3}\)P \(\rightarrow\) 3s\({}^{3}\)S & - & - \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Detected peaks for the AC-PPP reactor with CO\({}_{2}\) gas. Rotational, Vibrational, and Excitation Temperatures  
As indicated, the OH emission band \(\left(A^{2}\Sigma\to X^{2}\Pi\right)\) was detected in the wavelength ranges of 306-312 nm. The formation of the \(\cdot\)OH radical is generally caused by water vapor molecules that are present as impurities in the gas [35; 36]. The rotational, vibrational, and electronic states of this radical are populated by inelastic collisions with particles within the plasma (heavy particles and electrons) which produce variations in their energies. The rotational temperature gives the population distribution of rotational states. For these states, which have a small separation in energy, the effect of collisions with heavy particles are predominant; the population of rotational states is given by the energy of these particles. In equilibrium conditions, the rotational temperature is considered a good approximation of the gas temperature (mean kinetic temperature of heavy particles). On the other hand, the population of vibrational and electronic states, with higher energy separation, is given mainly by collisions with electrons. In this case, the obtained vibrational and excitation temperatures can be considered a closer approximation to the electron temperature.