We have recorded very-high-resolution photoelectron spectra of the inner-va
lence structure of CO+, excited with synchrotron radiation, and have resolv
ed fine structure never previously observed. Recently presented resonant An
ger decay spectra (Sundin et al 1997 Phys. Rev. A 56 480, 1997 J. Phys. B:
At. Mol. Opt. Phys. 30 4267) have established the energy of two-hole one-pa
rticle Rydberg states, and a comparison with these has been made to explain
some details of the spectra.