Spectroscopy and coherence lifetime extension of hyperfine transitions in 151Eu3+:Y2SiO5

We report a low-temperature spectroscopic characterization of the ground-state hyperfine transitions in Eu-151(3+):Y2SiO5 via coherent Raman scattering. Inhomogeneous linewidths of 21 and 38 kHz were measured for the I-z = +/- 1/2 <-> +/- 3/2 and the +/- 3/2 <-> +/- 5/2 ground-state transitions, respectively. Spin-echo decays were recorded for the I-z = +/- 1/2 <-> +/- 3/2 transition at zero field and for a small static magnetic field. In the latter case, analysis by a simple model gave an amplitude of 284 Hz and a correlation time of 3.5 ms for the transition frequency fluctuations. Application of a dynamical decoupling sequence resulted in coherence lifetimes up to 474 ms, an 18-fold increase compared to the spin intrinsic phase memory time of 26 ms.