The $F=3\mathrm{}$ to $F=2\mathrm{}$ hyperfine transitions in the $1s$ ground state of the two isotopes ${}^{185}{\mathrm{Re}}^{74+}$ and ${}^{187}{\mathrm{Re}}^{74+}$ were measured to be $(4560.5\mathrm{}\pm 3)\AA$ and $(4516.9\mathrm{}\pm 3)\AA ,$ 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 ɛ=2.23(9)% and 2.30(9)% are found for ${}^{185}\mathrm{Re}$ and ${}^{187}\mathrm{R}\mathrm{e},$ 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 $〈r_m^2{〉}^{1/2}=7.57\mathrm{}\left(32\right)\mathrm{}$ fm and $〈r_m^2{〉}^{1/2}$=7.69(32) fm for ${}^{185}\mathrm{Re}$ and ${}^{187}\mathrm{R}\mathrm{e},$ respectively, is inferred from the data. These radii are larger than the nuclear charge distribution radius $[〈r_c^2{〉}^{1/2}=5.39\mathrm{}(1)\mathrm{}$ 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.

• Received 12 August 1997

DOI:https://doi.org/10.1103/PhysRevA.57.879