6533b7d3fe1ef96bd12611ec

RESEARCH PRODUCT

Nuclear Charge Radius ofBe12

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