The 4s–3d and 5s–4d Rydberg complexes of O2 have been observed by (2+1) resonance-enhanced multiphoton ionization spectroscopy. All states show sharp rotational structure. Vibrational analysis (and rotational analyses of two bands) shows that all observed states are purely Rydberg in character with no detectable perturbations. Photoelectron spectra of the more intense peaks show the Δv=0 transition to be dominant, but large contributions from Δv≠0 transitions are observed and attributed to features in the ionization continuum. The Δv≠0 transitions are relatively weak for bands ascribed to excitation of a 3dδ Πg state and provide a method for producing nearly pure vibrational preparations (v+=0–3) of O+2 ions in the ground electronic state. Large amounts of O+ ions are observed and possible mechanisms of formation are discussed.
The 3dδ 1Φg and 3Φg Rydberg states of O2 have been observed by (2+1) resonant enhanced multiphoton ionization from the metastable a 1Δg state and the resulting spectra rotationally analyzed. In contrast to all other observed Rydberg states of O2, the 3Φ2, 3Φ3, and 3Φ4 states show no sign of perturbation or predissociation by valence states. The 1Φ3 state is apparently weakly predissociated. The energy level structure of those 3d Rydberg states which have been reliably assigned is compared with theoretical calculations. The reasons for the failure to detect Πg states in these experiments are discussed.
Mass-resolved, two-photon resonant, three-photon ionization of jet-cooled Cl2 has been used to study the spectroscopy and photophysics of the lowest energy, double-well 1Πg and 3Πg states of mixed Rydberg (4sσ) and ion-pair character. Inner well levels from v′=0 (64 027 cm−1) to v′=15 (73 343 cm−1) have been observed for 1Πg of the mass 70 molecular chlorine isotope. Inner well levels for 3Πg have been observed from v′=0 at 63 472 cm−1 to the top of the barrier, and well beyond that to levels spanning both wells. Observation of these long progressions is attributed to excitation via a repulsive continuum at a well-phonon level. The photophysics of this latter process as well as the mechanism for copious atomic ion formation are discussed. Variation of linewidth with vibrational quantum number due to the predissociation of inner well levels is observed and attributed to repulsive valence states. The data are in good agreement with the theoretical calculations of Peyerimhoff and Buenker, and Tuckett and Peyerimhoff.
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