Hyperfine interaction in ground and excited states of praseodymium-doped yttrium orthosilicate

We present characterization of the hyperfine interaction for the ground ${(}^3{H}_4)$ and one optically excited state ${(}^1{D}_2)$ of praseodymium impurities in a yttrium orthosilicate crystal. The Zeeman and pseudoquadrupole tensors were inferred by measuring the hyperfine splittings while rotating the direction of a weak $\left(\sim 40\hspace{0.5em}\mathrm{G}\right)$ magnetic field. The hyperfine spectra were recorded using Raman-heterodyne spectroscopy, a rf-optical double resonance technique.