Comparative study of core-excitation processes of C(1s) in CO, CO₂, OCS and CS₂molecules by electron impact

Abstract

In the present work, the distorted-wave approximation is applied to study the excitation of core-level electrons in OCS, CO2, CO and CS2 molecules by electron impact. More specifically, we report calculated differential and integral cross sections for the X1 Σ+ →1,3 Π transitions in an incident energy range of 300–800 eV. We also report the ratios of these cross sections for the corresponding transitions leading to the triplet and singlet core-excited states as a function of incident energy. These ratios are compared with the available experimental results for CO2 and CO molecules obtained by both conventional energy-loss spectroscopy and the ejected-electron detection technique. The results confirm the existence of a broad resonance for CO2 and CO molecules. Moreover, the good qualitative agreement between the calculated and experimental ratios shows that the decays of the autoionizing states are impact-energy independent. Quantitative agreement between theory and experiment is also satisfactory.

Study of inner-shell excitation processes from N(1s) orbitals in N2O molecules by electron impact

“…The physical origin of such discrepancies was also discussed. Moreover, the calculated RI(1:3) ratios for transitions involving the different atomic sites are very similar far from the resonance region, which seems to support our previous studies for molecules such as CO 2 , OCS, CS 2 and CO [22,23] that the nonresonant excitation cross sections are nearly independent of the valence excited orbital to where the core electron is promoted. On the other hand, the resonant core-excitation processes are highly dependent on both the hole and the particle wavefunctions.…”

“…Although the interchannel coupling effects are not taken into account in the DWA, the one-electron-resonance phenomenon (shape resonance) is represented in the collisional dynamics. As part of systematic studies, we have recently applied the DWA to investigate K-shell core-excitation processes in several molecules [20][21][22][23].…”

“…In general, we have found that the calculated results of generalized oscillator strength (GOS) as well as the RD(1:3) and RI(1:3) ratios are in good agreement with the available theoretical and experimental data. More specifically, in two comparative studies of electron-impact carbon K-shell excitation of the outer-valence isoelectronic molecules CO 2 , CS 2 and OCS [22,23], it was seen that the excitation cross sections as well as the RD(1:3) and RI(1:3) ratios of these targets are quite similar, particularly at high incident energies. This observation can probably be explained by the fact that carbon K-shell orbitals in these molecules are essentially atomic, and therefore they are very similar in the above targets.…”