The electric quadrupole hyperfine structure splitting constants B of the Eu isotopes 145–147, 151–153 were measured with collinear laser ion beam spectroscopy in 17 different transitions. From 105 experimental data B values of all levels in Eu ci 4${\mathit{f}}^7$${(}^8$S)5${\mathit{d}}^9$${\mathit{D}}_{\mathit{J}}$, ... 6p(7/2;1/2${)}_{\mathit{j}}$ and .... 6p(7/2;3/2${)}_{\mathit{J}}$ were determined in enhanced accuracy. The ratio ${}_{}{}^{151}{}_{}{}^{}$B${/}^{153}$B=0.39184(22) (mean value) significantly deviates from values of muonic measurements but is in good agreement with other atomic one in Eu i and Eu ii. Values for the ratios of quadrupole moments are given.

• Received 9 September 1992

DOI:https://doi.org/10.1103/PhysRevLett.70.541