An ab initio treatment of the X-ray emission spectra of the HCl molecule

Ab initio calculations for the energy and absolute transition rates of X-ray transition processes associated with the hydrogen chloride molecule have been undertaken at the relaxed Hartree-Fock level. Data for K-, L1- and L2 3-shell X-ray emission spectra are presented. Comparison with atomic calculations is used to show that the molecular effect is manifested most clearly in transitions involving the 5 sigma bonding molecular orbital. The spectra are, however, dominated by intra-atomic effects. Participator and spectator satellite transitions associated with an initial K-shell hole and a 3 pi excited valence electron are also considered. The energy and transition rate results for spectator satellites associated with the (1 sigma )3 pi resonant excited neutral state are close to those determined for the normal Kalpha and Kbeta processes. The 3 pi participator satellite is predicted to be at higher photon energy with 10% of the main Kbeta spectator line intensity

An ab initio study of the chlorine x-ray emission spectra of the CH3Cl molecule

The x 10ray emission processes associated with K, L1, and L2,3 chlorine core shell ionization in the CH3Cl molecule have been studied using ab initio molecular orbital methods. The energy and absolute transition rates of XES processes have been calculated. Comparison with atomic calculations is used to identify weak molecular effects. For the K;2 spectrum relaxation terms must be included to obtain good agreement between the calculated and experimental spectra. It is concluded that three transitions are major contributors to the K;2 spectrum. However, a one 10center model is adequate to account for the K;1 spectrum. Uncertainty regarding the extent of satellite contribution to the experimental L2,3 spectrum and the breakdown of the single particle model has made direct comparison between theory and experiment difficult. New measurements and a more refined theoretical approach beyond the relaxed Hartree 13Fock model are desirable. The L2,3 and L1 or K;2 emission spectra provide complementary information for probing the valence electronic structure of the CH3Cl molecule

X-ray emission spectra of some carbon-containing molecules

Ab initio molecular orbital calculations for the energy and intensity of X-ray transitions associated with the carbon monoxide, hydrogen cyanide and carbon dioxide molecules have been calculated at the Hartree-Fock level. It is demonstrated that in general the absolute transition probabilities are sensitive to the inclusion of electronic relaxation effects and interatomic transition moment contributions. It is concluded that calculations for molecular X-r!ly emission henomena should be undertaken at least at the multicentre relaxed Hartree-Fock level to achieve a realistic basis for comparison with experiment. Total carbon-K X-ray rates do not show a strong variation with changes in the molecular environment. The total rates are of a similar magnitude to those reported for the atom. The calculated carbon-K fluorescence yield is also similar in both the carbon atom and the CO2 molecule

X-RAY EMISSION PROCESSES FOR MOLECULES : AN AB INITIO STUDY FOR THE N2O MOLECULE

The oxygen and nitrogen X-ray spectra for the N2O molecule have been calculated using an ab initio molecular orbital method at the relaxed Hartree Fock level. Transition rates include interatomic contributions. The central and terminal nitrogen atom spectra are separately identified. Comparison with the experimental spectrum reveals the extent of satellite contamination in the electron impact excited spectrum

X-ray emission processes for molecules : An AB Initio study for the N2O molecule

The oxygen and nitrogen X-ray spectra for the N2O molecule have been calculated using an ab initio molecular orbital method at the relaxed Hartree Fock level. Transition rates include interatomic contributions. The central and terminal nitrogen atom spectra are separately identified. Comparison with the experimental spectrum reveals the extent of satellite contamination in the electron impact excited spectrum

AUGER ELECTRON SPECTRA FOR THE FLUOROMETHANES

The carbon and fluorine Auger spectra for the fluoromethane series of molecules, CH4-nFn, n=1...4, have been calculated using a semi empirical molecular orbital model. The model is satisfactory for the prediction of the spectral shape profiles, however energy shifts to account for hole-hole electronic relaxation and localization effects, especially on the fluorine atom, are warranted.The previous analysis for CF4 by Rye and Houston using only two values for the hole-hole interaction energy term is shown to be inadequate