Isotope shift measurements in the 2s1/2 → 2p3/2 transition of Be+ and extraction of the nuclear charge radii for 7,10,11Be

We have performed isotope shift measurements in the 2s1/2 → 2p3/2 transition of Be+ ions using advanced collinear laser spectroscopy with two counter-propagating laser beams. Measurements involving a frequency comb for laser stabilization and absolute frequency determination allowed us to determine the isotope shifts with an accuracy of 2 MHz. From the isotope shifts between 9Be and 7, 10, 11Be, high-accuracy mass shift calculations and the charge radius of the reference isotope 9Be we determined nuclear charge radii for the isotopes 7, 10Be and the one-neutron halo nucleus 11Be. The results are compared to nuclear-structure calculations using the fermionic molecular dynamics model which reproduce well the general trend of the radii. Decreasing charge radii from 7Be to 10Be are explained by the cluster structure of the nuclei. The increase from 10Be to 11Be is mainly caused by the halo neutron by which the 10Be core moves relative to the center of mass. Polarization of the 10Be core has only a small influence on the charge radius. © 2010 IOP Publishing Ltd