Interference effects during the Auger decay of theC∗O1s−1π∗resonance studied by angular distribution of theCO+(A)photoelectrons and polarization analysis of theCO+(A−X)fluorescence

Angular distributions of the ${\text{CO}}^{+}(A\text{ }^{2}\ensuremath{\Pi})$ photoelectrons and of the ${\text{CO}}^{+}(A\text{ }^{2}\ensuremath{\Pi}\ensuremath{\rightarrow}X\text{ }{^{2}\ensuremath{\Sigma}}^{+})$ fluorescence are computed in the vicinity of the $1{s}^{\ensuremath{-}1}{\ensuremath{\pi}}^{\ensuremath{\ast}}$ resonant excitation of the ${\text{C}}^{\ensuremath{\ast}}\text{O}$ molecule. In the calculations, lifetime vibrational interference and the direct transition amplitude for population of the $A\text{ }^{2}\ensuremath{\Pi}({v}^{\ensuremath{'}})$ states were taken into account ab initio. The weak direct photoionization channel induces broad exciting-photon energy range dispersions of the angular distribution parameters ${\ensuremath{\beta}}_{A}^{e}(\ensuremath{\omega})$ and $\ensuremath{\beta}{2}_{A}^{X}(\ensuremath{\omega})$, and the nuclear vibrational motion causes variations of the computed parameters across the positions of the ${\text{C}}^{\ensuremath{\ast}}\text{O}({v}_{r})$ vibronic states. Present calculations are in good agreement with available vibrationally and angularly resolved resonant Auger spectra. Theoretical $\ensuremath{\beta}{2}_{A}^{X}(\ensuremath{\omega})$ parameters are in agreement with the experimental results from the polarization analysis of the ${\text{CO}}^{+}(A\text{\ensuremath{-}}X)$ fluorescence induced by linearly polarized synchrotron radiation.