Large impact of the weak direct photoionization on the angularly resolved CO⁺(<i>A</i> ²Π) de-excitation spectra of the CO*(1σ⁻¹2π) resonance

Abstract

Abstract\nof the weak direct photoionization on angularly resolved CO + (A 2 ?) de-excitation spectra of the CO * (1? ?1 2?) resonance Abstract. Interference between the direct and resonant amplitudes for the population of the CO + (A 2 ?) state in the vicinity of the O 1s ? 2? excitation of CO * is studied by an ab initio theoretical approach. The weak direct photoionization induces Fano-Shore type profiles resulting in long-range exciting-photon energy dependencies of the computed angular distribution parameters for the CO + (A 2 ?) photoelectrons, ? e A (?), and for the subsequent CO + A 2 ? ? X 2 ? + fluorescence, ?2 X A (?). In the presence of the direct photoionization, the lifetime vibrational interference causes substantial variations of the computed parameter ? e A (?) across the positions of the CO * (v r) vibronic states. Theoretical results are in qualitative agreement with the vibrationally and angularly resolved CO + (A 2 ?) resonant Auger electron spectra recorded in the Raman regime at different exciting-photon energies across the CO * resonance.