ULTRASHORT-LIVED NON-RYDBERG DOUBLY-EXCITED RESONANCES IN DIATOMIC-MOLECULES

The CO+ emission systems A-X and B-X have been studied using monochrom atic photon excitation in the 20-34 eV. The vibrational branching rati os (v'= 4,5)/(v'= 3,2) for the A-X system were found to remain essenti ally constant within this excitation range, while the (v'= 1,2)/(v'= 0 ) branching ratios for the B-X system show a 40% variation. These resu lts are interpreted using quasidegenerate many-body perturbation theor y in terms of non-Rydberg doubly excited resonances in CO, which rapid ly autoionize to various low-lying CO+ states. It is suggested that so me earlier observed variations in the photoionization branching ratios for the v' = 0-2 levels of the CO+ X-2 Sigma(+) have the same origin.