Role of screening and angular distributions in resonant x-ray emission of CO

Resonantly excited carbon and oxygen x-ray-emission spectra of gaseous carbon monoxide are presented. Emission spectra obtained with selective excitation to the ${\mathrm{\pi }}^{\mathrm{*}}$ valence orbital and to various Rydberg levels are compared to satellite-free nonresonant spectra. Screening effects caused by the excited electron, creating energy shifts and intensity variations in the resonant spectra compared to the nonresonant spectra, are observed, as well as an angular dependence of the resonantly excited spectra. The experimental spectra are compared to simulated spectra where the vibronic part is computed by means of a lifetime-vibrational interference formalism. The electronic intensities are analyzed by a separate-state, self-consistent-field method and a formalism for resonant inelastic x-ray scattering, focusing on screening and angular dependence.