Quasi-metastable quartet levels in alkalilike atoms and ions

Evidence for Pauli exchange leading to excited-state enhancement in electron transfer

Single- and double-electron transfer to autoionizing 1s2l2l(') configurations in fluorine ions have been investigated for 1.1 MeV/u collisions of F7+ and F8+ with He and Ne. The resulting Auger electron emission spectra show anomolously large intensities for the formation of the metastable 1s(2s2p 3P) 4P state compared to the similarly configured 1s(2s2p 3P) 2P- and 1s(2s2p 1P) 2P+ states. The large 4P intensity, which cannot be explained on the basis of spin statistics, is attributed instead to the Pauli exchange of similarly aligned electrons.

Extreme-ultraviolet fluorescence from core-excited levels of neutral rubidium

Strong extreme-ultraviolet fluorescence originating from core-excited autoionizing levels of neutral Rb is observed. Radiative branching ratios approaching unity are inferred from the radiative yields. Long autoionizing lifetimes and fast radiative rates make these levels promising candidates for extreme-ultraviolet laser systems.

Identification and oscillator-strength measurement of the 109.1-nm transition in neutral Cs

The 109.1-nm transition in neutral Cs is the prototype of a class of transitions that originate from doubly excited quasi-metastable quartet levels. In this Letter we describe experiments that use tunable VUV radiation to determine the identity of this transition, to measure its oscillator strength, and to estimate its hyperfine splitting.