SPECTROSCOPY AT THE HIGH-ENERGY ELECTRON-BEAM ION-TRAP (SUPEREBIT)

The following progress report presents some of the X-ray measurements performed during the last year on the Livermore SuperEBIT facility. Th e measurements include: direct observation of the spontaneous emission of the hyperfine transition in ground state hydrogenlike holmium, Ho- 165(66+); measurements of the n = 2 --> 2 transition energies in neonl ike thorium, Th80+, through lithiumlike thorium, Th87+, testing the pr edictions of quantum electrodynamical contributions in high-Z ions dow n to the 0.4% level; measurements of the isotope shift of the n = 2 -- > 2 transition energies between lithiumlike through carbonlike uranium , (233)U(89+...86+)and U-238(89+... 86+), inferring the variation of t he mean-square nuclear charge radius; and high-resolution measurements of the K-alpha radiation of heliumlike xenon, Xe52+, using a transmis sion-type crystal spectrometer, resolving for the first time the 1s2p( 3)P(1)--> 1s(21)S(0) and 1s2s(3)S(1)--> 1s(21)S(0) transitions individ ually.