Magic-angle line narrowing in optical spectroscopy

Spin decoupling and line narrowing are observed for the first time in an optical transition, H43a "D21 of Pr3+ in LaF3 at 2A°K, with use of optical free-induction decay. The F19 nuclei, when irradiated by an appropriate rf field, undergo forced precession about an effective field at the magic angle in the rotating frame. The fluctuating F19-F19 dipolar interaction is thereby quenched and the optical linewidth drops from ∼10 to ∼2 kHz, as predicted in a theory of spin diffusion. © 1979 The American Physical Society.