Knowledge Bank

Using a combination of pulsed and cw dye lasers to excite a beam of NO molecules, we have measured autoionization rates for a number of levels in the 4f complex, in the v=3 vibrational level. These states lie a few hundred $cm-1$ above the ionization potential for v=0, and can ionize only via $\Delta$v=-3. Since previous spectroscopic analyses indicate that the 4f Rydberg electron exhibits essentially no core penetration, one would expect little of the configuration interaction in the core region that normally gives rise to autoionization. Nonetheless, autoionization rates ranging from about 20 psec to 200 psec are observed, with a strong and complicated dependence on core rotation and the projection of L on the rotational axis. The autoionization is probably mediated by the long range interaction of the Rydberg electron with the multipole moments of the $NO+$ core, a mechanism recently postulated by Herzberg and $Jungen.1$ Analysis of this process is in progress, and it is likely that similar effects occur in the Rydberg states of many molecules, leading to much shorter lifetimes than were previously predicted.