Determination of theEu153-Eu151quadrupole-moment ratio by excited-state optically detected nuclear magnetic resonance

Excited-state optically detected nuclear-magnetic-resonance signals have been observed in a ${\mathrm{Eu}}^{3+}$ center for what we believe to be the first time. There is negligible pseudoquadrupolar contribution to the quadrupole splitting in the ${}_{}{}^5{}_{}{}^{}D_0^{}{}_{}{}^{}$ excited state and the ratio of the resonant frequencies is consequently equal to the ratio of the electric quadrupole moments of the two naturally abundant europium isotopes. This ratio of the ${}_{}{}^{153}{}_{}{}^{}\mathrm{Eu}$ and ${}_{}{}^{151}{}_{}{}^{}\mathrm{Eu}$ quadrupole moments is determined to be 2.556±0.005.