# Extended Photoionization Cross Section Calculations for C III
## 3 Discussion  
We report an extensive and elaborate theoretical study of atomic properties for CIII. We have applied systematic methods to the computation of transition data and photoionization cross sections. This study implies the electron-impact excitation of C IV and photoionization of CIII. For the electron impact excitation, we concentrated on 105 transitions from 15 target levels, finding 5929 collision strengths. The photoionization calculation of CIII has been computed for ground and excited states, accounting for radiative and Auger damping. We find good agreement in the calculated weighted oscillator strengths with the experiment. The unified approach of the R-matrix method in intermediate coupling, with and without damping, allowed us to examine in detail not only the individual structure of the autoionizing doubly excited states, but also collectively in the autoionization series. The resonances appearing for photoionization of C III 2s\({}^{2}\) \({}^{1}\)S ground states at 3.51 Ry, below the \begin{table}
\begin{tabular}{c c c c} \hline
**2s2(\({}^{1}\)S) – 1s\({}^{2}\)2s2p\({}^{1}\)P\({}_{1}\)o** & \multicolumn{2}{c}{**2s2(\({}^{1}\)S) – 1s\({}^{2}\)2s3p \({}^{1}\)P\({}_{1}\)o**} \\
**Source** & **gf\({}^{1}\)** & **Source** & **gf\({}^{1}\)** \\ \hline [PERSON] et al. [55] & 0.787 & [PERSON] [48] & 0.241 \\ \hline [PERSON] and [PERSON] [49] & 0.757 & [PERSON], [PERSON] [27] & 0.240 \\ \hline Source & lifetime(ns) & Source & lifetime(ns) \\ \hline Experiment & \multicolumn{2}{c}{Experiment} \\ \hline [PERSON] et al. [46] & 0.57 \(\pm\) 0.02 & [PERSON] and [PERSON] [56] & 0.28 \\ \hline [PERSON]. [55] & 0.50 \\ \hline Others & 0.66 \\ \hline [PERSON] and [PERSON] [56] & 0.572 \\ \hline [PERSON] et.al. [57] & 0.53 \\ \hline Theory & \multicolumn{2}{c}{Theory} \\ \hline Present & 0.5399 & Present & 0.290 \\ \hline [PERSON] [47] & 0.559 & [PERSON], [PERSON] [27] & 0.251 \\ \hline [PERSON]; [PERSON] [27] & 0.5651 & [PERSON], [PERSON] [58] & 0.265 \\ \hline [PERSON], [PERSON] [58] & 0.4648 \\ \hline \end{tabular}
\end{table} 
Table 4: _Cont._ \begin{table}
\begin{tabular}{c c c c c c c c} \hline
**State** & **\(\Gamma\)(Ry)** & **\(\Gamma\)(Ry)** & **\(\Gamma\)(Ry)** & **State** & **\(\Gamma\)(Ry)** & **\(\Gamma\)(Ry)** & **\(\Gamma\)(Ry)** \\
**2p\({}^{3}\)2 ns (\({}^{1}\)P\({}^{0}\))** & **Ref. [54]** & **Ref. [28]** & **Present** & **2p\({}^{3}\)2 nd (\({}^{1}\)P\({}^{0}\))** & **Ref. [55]** & **Ref. [29]** & **Present** \\ \hline
5 & 9.57\({}^{-03}\) & 1.04\({}^{-02}\) & 1.028\({}^{-02}\) & 4 & 3.07\({}^{-03}\) & 3.82\({}^{-03}\) & 3.56\({}^{-03}\) \\ \hline
6 & 5.09\({}^{-03}\) & 5.43\({}^{-03}\) & 5.95\({}^{-03}\) & 5 & 1.63\({}^{-03}\) & 2.13\({}^{-03}\) & 1.69\({}^{-03}\) \\ \hline
7 & 3.07\({}^{-03}\) & 3.23\({}^{-03}\) & 3.60\({}^{-03}\) & 6 & 9.52\({}^{-04}\) & 1.32\({}^{-03}\) & 1.11\({}^{-03}\) \\ \hline
8 & 1.99\({}^{-03}\) & 2.057\({}^{-03}\) & 1.98\({}^{-03}\) & 7 & 6.05\({}^{-04}\) & 8.08\({}^{-04}\) & 6.94\({}^{-04}\) \\ \hline
9 & 1.36\({}^{-03}\) & 1.39\({}^{-03}\) & 1.60\({}^{-03}\) & 8 & 4.06\({}^{-04}\) & 5.878\({}^{-04}\) & 4.607\({}^{-04}\) \\ \hline \end{tabular}
\end{table} 
Table 5: Comparison of calculated resonant widths (\(\Gamma\) in Ry) of _2 pns_\({}^{1}\)P\({}^{o}\) and _2 pnd_\({}^{1}\)P\({}^{o}\) autoionizing states of C III (\(a^{\text{b}}\) reads \(a\times 10^{\text{b}}\)). photoionization threshold of metastable states at 3.62 Ry, shown in Figure 3, are associated with the photoionization of 1s\({}^{2}\)2s2p 1\({}^{\rm{po}}\) metastable state. The resonances appearing within the 3.62 Ry and 4.1 Ry photon energy range are caused by the photoionization of the C III 2s\({}^{2}\)1S ground state. Two autoionizing series, 2p\(ns^{\rm{1}}\)Po and 2p\(nd\) 1\({}^{\rm{po}}\), are discernible.