CROSS-RELAXATION PROCESS BETWEEN -EARTH IONS IN LIYF4 CRYSTALS(3 RARE)

The cross-relaxation probability (sec(-1)) involving the S-5(2) and I- 5(8) levels of holmium ions in LiYF4 was investigated and its concentr ation dependence determined. By using a random distribution function o f ions in the crystal, it was possible to determine the concentration dependence of the nonradiative probability for the ion-ion energy tran sfer by dipole-dipole, dipole-quadrupole, and quadrupole-quadrupole el ectric interactions. The applied model shows that the ion-ion cross-re laxation transfer between Ho3+ ions in LiYF4 crystals, cannot account for the experimental results. At a high concentration level of activat ors (>1%), the excited ion must interact with two neighbors of same sp ecie competing with the single ion cross-relaxation transfer.