Measurement of electron spin-spin relaxation by an optical labeling technique

Abstract

The electron spin-spin relaxation due to flip-flop of like spins, which cannot be detected by magnetic methods, was measured by optical means for the first time in ruby (0.05 wt.%). Irradiation with a narrow-band laser produces an internal nonequilibrium in the ground-state spin system (${S}_{z}=\ifmmode\pm\else\textpm\fi{}\frac{1}{2}$ levels in $^{4}A_{2}$) and recovery from the nonequilibrium by spin-spin relaxation is measured by monitoring the time evolution of the optical holes. The observed spin-spin relaxation time (~0.5 ms) was much longer than the transverse decay time estimated from electron spin-echo decay. The spin-spin relaxation in dilute ruby (0.0034 wt.%) was too slow to be observed.