(2+1) RESONANCE ENHANCED MULTIPHOTON IONIZATION OF HYDROGEN-CHLORIDE IN A PULSED SUPERSONIC JET - SPECTROSCOPY AND RYDBERG-APPROXIMATELY-VALENCE INTERACTIONS OF THE 1-EPSILON+(0+) AND 3-EPSILON-(1, 0+) STATES .2.

We report a spectroscopic study of the 1Σ+(0+) and 3Σ-(1, 0+) Rydberg states as well as the V1Σ+(0+) valence state of hydrogen chloride using (2 + 1) resonance enhanced multiphoton ionization (REMPI). Pulsed supersonic expansion techniques and time-of-flight mass spectrometry (TOFMS) facilitate rotational analysis of both H35Cl and H37Cl isotopomers. Many new bands are characterized, including the v′ = 3 to 32 vibrational levels of the V1Σ+(0+) state. Multiphoton excitation spectra from the v′ = 0 level of the X1Σ+(0+) state through the lowest vibrational levels of the V1Σ+(0+) state suggest non-Franck-Condon transitions. Perturbations in intensity, line position, and rotational constant are consistent with Rydberg ∼ valence mixing between the short range 1Σ+(0+) and 3Σ-(0+) Rydberg states and long range V1Σ+(0+) state. The simultaneous detection of molecular and fragment ion yields is attributed to superexcited electronic states. The onset of distinct H+ and Cl+ ion yield channels indicates the presence of dissociation paths at the three-photon energy and at relatively large internuclear distance. © 1991.