MEASUREMENT OF QED AND HYPERFINE SPLITTING IN THE 2S(1 2)-2(P3/2) X-RAY TRANSITION IN LI-LIKE BI-209(80+)/

A measurement of the 2s(1/2)-2p(3/2) x-ray transition in trapped Li-li ke Bi80+ ions was made that resolved the 0.820 +/- 0.026 eV hyperfine splitting of the (1s(2)2S)(F=4,5) ground configuration, providing the first such measurement in a multielectron highly charged ion. The inte nsity ratio of the two components is shown to be a new electron densit y diagnostic. The statistically averaged 2788.139 +/- 0.039 eV energy of the 2s(1/2)-2p(3/2) transition provides the most accurate test of Q ED in a high-Z ion to date, demonstrating the need for including highe r-order terms in the Lamb shift calculations.