2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/89110We report ultraslow group velocities of light in a solid. Light speeds as slow as 45 m/s were observed, corresponding to a group delay of 66 ms in a 3-mm thick crystal. Reduction of the group velocity is accomplished by using a sharp spectral feature in absorption and dispersion, produced by a Raman excited spin coherence in an optically dense Pr doped Y2SiO5 crystal.12 pages, 5 figuresQuantum Physicstext