Spectral-hole-burning study of the hyperfine interaction in axial ${\mathrm{Eu}}^{3+}$ centers in ${\mathrm{CaF}}_2$, ${\mathrm{SrF}}_2$, and ${\mathrm{BaF}}_2$

Hole-burning spectra of ${\mathrm{Eu}}^{3+}$ transitions in axial centers of alkaline-earth fluorides are presented. These spectra, along with optically detected nuclear-magnetic-resonance results, are used to analyze the hyperfine interactions in the ${}_{}{}^7{}_{}{}^{}\mathrm{F}_0^{}{}_{}{}^{}$ ground state and in the ${}_{}{}^5{}_{}{}^{}\mathrm{D}_0^{}{}_{}{}^{}$ optically excited state. The axial nature of these centers simplifed the theoretical analysis from which we obtained the nuclear-quadrupole-interaction strength and the nuclear-magnetic moment quenching factor. An improved value of the ratio of the quadrupole moments of ${}_{}{}^{153}{}_{}{}^{}\mathrm{Eu}$ and ${}_{}{}^{151}{}_{}{}^{}\mathrm{Eu}$ of 2.553±0.001 is also given.