Abstract
We report the measurement of what we believe to be the narrowest known optical resonance in a solid. This was made on the transition of : at 1.4 K using photon echoes with sufficiently low laser power to almost eliminate contributions from instantaneous diffusion. The optical resonance widths measured for ions in the two crystallographic sites of and in a magnetic field of 100 G are 122 Hz (site 1) and 167 Hz (site 2). These widths are dominated by population decay, but up to 20 Hz is attributed to spin fluctuations which have been reduced by the applied magnetic field.
- Received 26 October 1993
DOI:https://doi.org/10.1103/PhysRevLett.72.2179
©1994 American Physical Society