Comparative study of electron-impact C(1s) core-excitation processes in C2 and C2N2 molecules

Distorted-wave approximation (DWA) is applied to study core-orbital excitations in C2and C2N2 molecules by electron impact. More specifically, we report calculated integral cross sections (ICS) for the X1Σg+→1,3Πu(1sσu→1pπg) and X1Σg+→1,3Πg(1sσg→1pπg) transitions in the C2, and X1Σg+→1,3Πg(2sσg→2pπg) and X1Σg+→1,3Πu(2sσu→2pπg) transitions in the C2N2 molecules in the 300-800 eV incident energy range. The comparison of the calculated ICS of these targets with the corresponding data for C2H2 presented. Comparison is also made for the theoretical RI(3:1) ratios of these targets which are calculated by dividing the ICS for triplet transitions by the corresponding results for singlet transitions. The similarities and differences of these results, particularly the presence of the shape resonances at near excitation thresholds, are discussed. The influence of the atomic (localized) and molecular (delocalized) characters of the core orbitals on the core-excitation processes is also investigated. In addition, generalized oscillator strengths for the singlet core-orbital transitions are calculated at incident energy of 1290 eV for C2 and C2N2. A comparison with the existing theoretical and experimental data for C2H2 is also presented.