Trapped-ion technique for measuring the nuclear charge radii of highly charged radioactive isotopes

We present the first measurement to isolate the variation of nuclear effects in the x-ray transitions of few-electron heavy ions. Using a novel technique to produce and trap radioactive ions we measured the energy difference between 2s(1/2)-2p(3/2) transitions in Li-, Be-. B-, and C-like U-233 and U-238. We show that because of the simplified atomic structure of few-electron ions the data are readily interpreted in terms of the variation in the mean nuclear radius. A value delta[r(2)](233.238) = -0.457 = 0.043 fm(2) is found, which lies between earlier measurements based on different techniques.