Double core–hole correlation satellite spectra of N2 and CO molecules

We have theoretically investigated the correlation satellite spectra associated with the single-site (ss) and two-site (ts) double core–hole (DCH) states. The calculated ssDCH satellite spectra of N2 (N 1s−2) and CO (O 1s−2) reproduced the observed experimental spectra satisfactorily and provided the first detailed assignments. DCH spectroscopy using X-ray two-photon photoelectron spectroscopy (XTPPS) was examined taking account of the single core–hole (SCH) and DCH satellite spectra. The results demonstrate that in XTPPS the ssDCH satellite spectrum is separated from other SCH/tsDCH spectra, while the tsDCH states and their satellite states may be overlapped with the SCH satellite spectrum.