Nuclear Charge Radii of Be-7,9,10 and the one-neutron halo nucleus Be-11

Abstract

Nuclear charge radii of ${}^{7,9,10,11}$Be have been determined by high-precision laser spectroscopy. On-line measurements were performed with collinear laser spectroscopy in the $2s_{1/2}\to 2p_{1/2}$ transition on a beam of Be${}^{+}$ ions. Collinear and anticollinear laser beams were used simultaneously and the absolute frequency determination using a frequency comb yielded an accuracy in the isotope-shift measurements of about 1 MHz. Combination with accurate calculations of the mass-dependent isotope shifts yield nuclear charge radii. The charge radius decreases from ${}^7$Be to ${}^{10}$Be and then increases for the halo nucleus ${}^{11}$Be. When comparing our results with predictions of {\it ab initio} nuclear structure calculations we find good agreement. Additionally, the nuclear magnetic moment of ${}^7$Be was determined to be $-1.3995(5)\hat{I}{¼}_{\mathrm{N}}$ and that of ${}^{11}$Be from a previous ${\hat{I}}^2$-NMR measurement was confirmed.

4 pages, 2 figures calculated mass shift values have been re-evaluated with the latest mass values for the beryllium isotopes and the nuclear polarization contribution for Be-11, published by K. Pachucki et al. ater submission of our manuscript, is also included now