Nuclear magnetization distribution radii determined by hyperfine transitions in the 1s level of H-like ions 185Re74+ and 187Re74+

The F=3 to F=2 hyperfine transitions in the is ground state of the two isotopes Re-185(74+) and Re-187(74+) were measured to be (4560.5+/-3) Angstrom and (4516.9+/-3) Angstrom, respectively, using emission spectroscopy in an electron beam ion trap. After applying appropriate corrections for the nuclear charge distribution and QED effects, a Bohr-Weisskopf effect of epsilon=2.23(9)% and 2.30(9)% are found for Re-185 and Re-187, respectively. This value is almost twice that of a previous theoretical estimate, and indicates a distribution of the nuclear magnetization far more extended than that of the nuclear charge. A radius of the magnetization distribution of [r(m)(2)](1/2) = 7.57(32) fm and [r(m)(2)](1/2) = 7.69(32) fm for Re-185 and Re-187, respectively, is inferred from the data. These radii are larger than the nuclear charge distribution radius [[r(c)(2)](1/2) = 5.39 (1) fm] for both isotopes by factors 1.40(6) and 1.43(6), respectively. We find that the Bohr-Weisskopf effect in H-like ions is a sensitive probe of nuclear magnetization distribution, especially for cases where the charge distribution and magnetic moments are accurately known. [S1050-2947(98)02002-2].