Optical study of hyperfine coupling in theF07andD05states of twoEu3+centers inCaF2andCdF2

The hyperfine interaction in the ${}_{}{}^7{}_{}{}^{}\mathrm{F}_0^{}{}_{}{}^{}$ and ${}_{}{}^5{}_{}{}^{}\mathrm{D}_0^{}{}_{}{}^{}$ states in oxygen-compensated ${\mathrm{Eu}}^{3+}$ centers of $C_{3v}$ symmetry in ${\mathrm{CaF}}_2$ and ${\mathrm{CdF}}_2$ is reported. Optically detected nuclear-magnetic-resonance measurements determine (i) the hyperfine structure in the two states and (ii) their nuclear Zeeman splittings. In addition, optical hole burning is used to measure (iii) the quadratic electronic Zeeman effect on the ${}_{}{}^7{}_{}{}^{}\mathrm{F}_0^{}{}_{}{}^{}$→${\mathrm{}}^5$ ${\mathrm{D}}_0$ transition. These three measurements associated with both ${}_{}{}^{151}{}_{}{}^{}\mathrm{Eu}$ and ${}_{}{}^{153}{}_{}{}^{}\mathrm{Eu}$ isotopes are employed to determine the magnitudes and signs of the pseudoquadrupole interactions, of the quadrupole interactions, and of the effective nuclear magnetic moments. The quadrupole interaction parameters are found to be negative in the excited state but positive in the ground state. This has been confirmed using a double-radio-frequency experimental technique.