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

TL;DR

This study precisely measured the nuclear charge radii of Be isotopes, revealing a decrease from $^7$Be to $^{10}$Be and an increase at $^{11}$Be, aligning well with theoretical predictions and confirming magnetic moments.

Contribution

The paper provides high-precision laser spectroscopy measurements of Be isotopes' charge radii, including the halo nucleus $^{11}$Be, and confirms magnetic moments, advancing nuclear structure understanding.

Findings

Charge radius decreases from $^7$Be to $^{10}$Be.

Charge radius increases at $^{11}$Be, indicating halo structure.

Good agreement with ab initio nuclear structure calculations.

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 $-1.3995(5)\mu_{\rm N}$ and that of $^{11}$Be from a previous $\beta$-NMR measurement was confirmed.