Beam Fractions in the Lowest-Quartet Metastable Autoionizing State forO5+andF6+Beams after Passage through Foils

When fast beams of oxygen and fluorine ions are incident on carbon and metal foils thick enough to produce charge-state equilibrium, a significant portion of the lithiumlike beam fraction emerges in excited metastable autoionizing states. We have studied the yield of these states with beams in the range 2-20 MeV incident on nominal ${10-\mathrm{\mu }\mathrm{g}/\mathrm{c}\mathrm{m}}^2$ carbon foils and on various metallic foils. The decay in flight of the lowest of these states, the $\mathrm{}\left(1s2s2p\right)\mathrm{}{}_{}{}^4{}_{}{}^{}P_{\frac{5}{2}}^0{}_{}{}^{}$, is monitored with observation of the spectrum of ejected electrons. We find, for example, that the maximum yield of this single state per incident beam particle is approximately 0.8% and 0.6% for oxygen and fluorine, respectively, on carbon. The energy dependences and target-material dependences are measured and discussed. Comparison is made to related work of Dmitriev et al.