Angle-resolved photoion yield and resonant Auger spectroscopy for the doubly excited Rydberg states above the C 1s threshold of CO

Doubly excited core-hole states of carbon monoxide in the photon energy region of 300-305 eV, i.e., directly above the C 1s ionization threshold, have been studied using both angle-resolved ion-yield and high-resolution resonant Auger spectroscopies. The leading configurations of the most prominent doubly excited Rydberg states are assigned by careful analysis of the ion-yield spectra and the final-state spectra to C 1 s-1 (5 σ-1 2 π1 S=1) 3sσ (v′ =0,1,2), C 1 s-1 (5 σ-1 2 π1 S=0) 3sσ (v′ =0,1,2), and C 1 s-1 (5 σ-1 2 π1 S=1) 4sσ (v′ =0,1), which can only be populated via a conjugate shake-up process. Analysis of the resonant Auger spectra provides an assignment of several two-hole-one-electron (2h-1e) final states.