SOLVED AND UNSOLVED PROBLEMS OF NEAR-THRESHOLD SPECTROSCOPY OF N-2 AND CO

Rotationally resolved jet absorption studies of N-2 at 800-850 Angstro m have led to detailed identifications of the electronic structures as sociated with low-J rovibrational thresholds of ground-state N-2(+). O f particular interest is a series of perturbed f complexes that intera ct with core-excited Rydberg levels and, possibly, with the b' valence state. The latter assumes the role of a core-excited Rydberg state at high energies and small internuclear distances. A similarly complete picture of the Rydberg structure of CO is still lacking. The interpret ation of l-uncoupling effects and, thus, the identification of Rydberg complexes is difficult owing to widespread perturbations by non-Rydbe rg levels. Significant advances have been made in the understanding of the Sigma-Sigma Rydberg-valence interactions, but few hard facts have emerged concerning the Pi-Pi interactions where the analysis proceeds in the near-total absence of guidance by theoretical calculations.