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.
The absorption spectra of hydrogen and deuterium have been measured in the range 91–98 nm. A narrowband extreme ultraviolet laser source is employed in combination with a molecular beam, allowing for sub-Doppler resolution and yielding linewidths of 0.23 cm−1. Transition frequencies of 291 lines of the Lyman and Werner bands are determined with an average absolute accuracy of 0.03 cm−1. The data are analyzed in a semi-empirical perturbation model, involving heterogeneous couplings between nearby lying levels of B1Σu+ and C1Πu states. This model is found to be accurate on the level of accuracy of the data obtained.
Sub-Doppler excitation spectra of HD have been recorded in the range 92 -98 nm with the use of a narrow-band and tunable extreme ultraviolet laser in combination with a molecular beam. Frequencies of 147 transitions to the B 'X", C 'Il", and EF 'X states have been calibrated with an average absolute accuracy of 0.035 cm '. The data have been analyzed in the framework of a semiempirical deperturbation model involving mutual couplings between nearby lying levels of the B 'X"+ and C 'II, states. Also, symmetrybreaking effects, i.e. , interactions with EF 'X gerade states, were inferred from the data.
In a laboratory investigation using tunable picosecond lasers in a pump-probe configuration, lifetimes of the E 1 P, and states of CO are experimentally determined. For E 1 P, , the lifetime is found to v ϭ 0 v ϭ 1 v ϭ 1 vary significantly for the isotopomers. Combining the data with existing oscillator strengths, predissociation probabilities within the range of 93.6%-98.6% result for C O, C O, and C O in the case of the E 1 P, 12 16 13 16 13 18 state, which is the state that predominantly influences the isotopic fractionation of CO in interstellar clouds. v ϭ 1
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