IDENTIFICATION OF THE NS-SIGMA AND ND-LAMBDA RYDBERG STATES OF O2 FOR N=3-5

The 4s-3d and 5s-4d Rydberg complexes of diatomic oxygen have been studied by (2 + 1) resonance-enhanced multiphoton ionization of the X3SIGMA(g)- ground state of O2. We have located and identified at least two vibrational levels of each of the following states: Three of four expected 4ssigma PI states; all four expected 5ssigma PI states; 18 of 22 expected 3d states (with only the states of the 3dsigma orbital remaining unobserved); and 5 of the 10 predicted 4dpi states. State assignments were assisted by the following: the results of rotational cooling and laser polarization experiments which facilitated the rotational analysis, band positions, band intensities, and parameterized calculations. The experimentally determined state locations are compared with the state locations obtained from ab initio calculations. We have carried out isotope experiments and rotational linewidth analysis to study in some detail the mixing between the Rydberg states and the repulsive valence states as well as the mixing between the Rydberg states themselves. We conclude that direct predissociation dominates indirect predissociation as a dissociative mechanism, but there is evidence of DELTAv not-equal 0 interactions which perturb the rotational structure of the 3dpi SIGMA and DELTA states. The relative intensities of the states detected are found to span a range in excess of 10(4) with the nssigma PI states being the weakest and the ndpi SIGMA states being the strongest. Photoionization of the ndpi SIGMA states appears to be most affected by the shape resonance in the continuum. Our measurements confirm the expectation that many of the properties of the Rydberg states in the same series scale as (n*)-3.