Predominant dissociation of the CO*(D2Π)n(d/s)σ Rydberg states into atomic excited Rydberg fragments with the same effective principal quantum number

Dissociation of the CO molecule excited in the photon energy range between 20 eV and 25 eV is investigated by photon-induced fluorescence spectroscopy (PIFS) detecting dispersed fluorescence from C I* 2s 2 2p 1 n (d/s) fragments in the spectral range of 115–135 nm. First experimental indications were found for a predominant dissociation of the CO*(D 2 Π) n (d/s)σ Rydberg states into the Rydberg states of the neutral C I atom conserving the effective principal quantum number n * = n − δ of the Rydberg electron. Such a process has as yet been verified only for the dissociating molecular Rydberg series (c 4 Σ − u ) n (d/s)σ g 3 Σ − u in O* 2 (H Liebel et al 2000 Phys. Lett. 267 267). The selective dissociation of the molecular Rydberg states into atomic ones is interpreted by theoretical potential energy curves of the CO + ion and molecular orbitals of Rydberg electrons computed within the single-centre approach.