title: Rydberg-valence interactions of CO, and spectroscopic evidence characterizing the C' 1Sigma+ valence state.
abstract: Rotationally cold absorption and two-photon ionization spectra of CO in the 90-100 nm region have been recorded at a resolution of 0.3-1.0 cm(-1). The analyses of up to four isotopomers seek to clarify the observations in regions where the Rydberg levels built on the ground state X (2)Sigma(+) of the ion interact with valence states of (1)Sigma(+) and (1)Pi symmetry. Previous observations of the 3ssigma, B (1)Sigma(+) Rydberg state, reviewed by Tchang-Brillet et al. [J. Chem. Phys. 96, 6735 (1992)], have been extended to energies above its avoided crossing with the repulsive part of the D(') (1)Sigma(+) valence state where resonances of varying intensities and widths have been attributed to the fully coupled 3ssigma or 4ssigma and D(') potentials, and where the B state approaches a second avoided crossing with the C(') (1)Sigma(+) valence state [Cooper and Kirby, J. Chem. Phys. 87, 424 (1987); 90, 4895 (1989); Chem. Phys. Lett. 152, 393 (1988)]. Fragments of a progression of weak and mostly diffuse bands, observed for all four isotopomers, have been assigned to the C(')<--X transition. The least-squares modeling of the 4p and 5p complexes reveals the 3ppi, E (1)Pi Rydberg state to be one of the perturbers, violating the Deltav=0 selection rule for Rydberg-Rydberg interactions on account of its rapid transition with increasing v from Rydberg to valence state. A second (1)Pi perturber, very loosely bound and clearly of valence type, contributes to the confusion in the published literature surrounding the 5p, v=0 complex.
authors.affiliation: Observatoire de Paris, section de Meudon, LERMA, UMR 8112 du CNRS, 92195 Meudon Cedex, France.
authors.forename: Michèle
authors.initials: M
authors.lastname: Eidelsberg
authors.forename: Françoise
authors.initials: F
authors.lastname: Launay
authors.forename: Kenji
authors.initials: K
authors.lastname: Ito
authors.forename: Takashi
authors.initials: T
authors.lastname: Matsui
authors.forename: Paul C
authors.initials: PC
authors.lastname: Hinnen
authors.forename: Elmar
authors.initials: E
authors.lastname: Reinhold
authors.forename: Wim
authors.initials: W
authors.lastname: Ubachs
authors.forename: Klaus P
authors.initials: KP
authors.lastname: Huber