Transient spectral hole-burning studies of the R2 line in ruby

We report transient spectral hole-burning studies of the R2(±1/2) line in 130, 20 ppm and 0.6 ppm ruby between 2.4 and 70 K. The homogeneous line width Γh is found to be 142 ± 6 MHz at 2.4 K for both 20 and 130 ppm crystals; this value is in agreement with the T1 value of 1.1 ns (Γh = 1/2πT1 = 140 MHz) for the 2 A ¯ state obtained by Rives and Meltzer who used pulsed, non-selective laser excitation. The line width is dominated by a direct one-phonon relaxation process 2 A ¯ → E ¯ up to 50 K whereas at higher temperatures two-phonon Raman scattering becomes dominant. Cross-relaxation and spin-lattice relaxation times significantly affect pseudo-CW experiments.