Core-excited quasimetastable levels

This paper describes the properties of a class of core-excited atomic levels which have been termed quasimetastable. In alkali atoms and alkali-like ions, these levels autoionize at rates that are comparable to or slower than their radiative rates and, therefore, radiate intensely in the extreme UV. Because these rates are typically of the order of 10/sup 8/s/sup -1/, these levels accumulate substantial population. The paper describes three experiments based on the properties of these levels. In the first of these, a pulsed hollow cathode is used to populate the quasi-metastable 2p/sup 5/3s3p/sup 4/S/sub 3/2/ level of neutral Na. A tunable laser is used to transfer population to other levels in the quartet manifold. Laser-induced fluorescence is used to delineate fifteen levels and thirty transitions within the manifold