Measurement of the Quadrupole Moment of the First Excited2+State ofO18

We measured the static electric quadrupole moment ($Q_{2^{+}}$) and $B(E2, {0_1}^{+}\to {2_1}^{+})$ of the first excited state of ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ at 1.98 MeV. The values obtained were $(-0.19\mathrm{}\pm 0.02 \mathrm{b})e$ (for the positive sign of the interference term involving the $2_2^{+}$ state) and $(0.0048\mathrm{}\pm 0.0002 {\mathrm{b}}^2)e^2$ for $Q_{2^{+}}$ and $B(E2, {0_1}^{+}\to {2_1}^{+})$, respectively. For these values the ratio $\frac{\left|Q_{2^{+}}\right|}{{\left[B\right(E2, {0_1}^{+}\to {2_1}^{+}\left)\right]}^{\frac{1}{2}}}$ is about 3, whereas for no other nucleus does it exceed unity by more than 30%.