Resonant Optical Energy Transfer in Ruby

Measurements are reported of resonant nonradiative energy transfer in the $R_1$ line of ruby at 5 K using a fast Stark shifting technique. The transfer rate for 0.8% ruby is found to be slow, ∼ 1 ${\mathrm{msec}}^{-1\mathrm{}}$, contrary to the much more rapid rates proposed earlier by several workers but in fair agreement with the results of Heber. Implications of the results for the occurrence of an Anderson transition in ruby are discussed.