Nuclear Charge Radius of ${}^{12}$Be

Abstract

The nuclear charge radius of ${}^{12}$Be was precisely determined using the technique of collinear laser spectroscopy on the $2s_{1/2}\to 2p_{1/2,3/2}$ transition in the Be${}^{+}$ ion. The mean square charge radius increases from ${}^{10}$Be to ${}^{12}$Be by $\delta <r_{\mathrm{c}}^2{>}^{10,12}=0.69(5){\text{fm}}^2$ compared to $\delta <r_{\mathrm{c}}^2{>}^{10,11}=0.49(5){\text{fm}}^2$ for the one-neutron halo isotope ${}^{11}$Be. Calculations in the fermionic molecular dynamics approach show a strong sensitivity of the charge radius to the structure of ${}^{12}$Be. The experimental charge radius is consistent with a breakdown of the N=8 shell closure.

Comments: 5 pages, 3 figures