Migration of energy between Yb3+ ions in garnet crystals

The time and temperature dependences of the probability of deactivation of the excited state of the Yb³⁺ ions in mixed yttrium-ytterbium garnets of various compositions were investigated in the temperature range 1.7–300°K. An analysis indicated that these dependences were governed by the excitation energy migration, which was the "bottleneck" in the process of nonradiative deactivation of the excited state. A strong rise (by more than an order of magnitude) of the migration probability was observed when the temperature was raised from 1.7 to 4.2°K. The diffusion theory, applicable to migration processes in the case of homogeneous broadening of spectral lines, was generalized to inhomogeneous broadening. The theoretical results were in good agreement with the experimental data.