Diffusion and Transfer of Optical Excitation in YF3: Yb, Ho

An experimental investigation has been made into the nature of the decay of excited ${\mathrm{Yb}}^{3+}$ donors in the presence of ${\mathrm{Ho}}^{3+}$ acceptors in Y${\mathrm{F}}_3$. The results imply that the mechanism of donor-acceptor energy transfer is based on electric dipole-dipole interaction. As the donor concentration is increased, three regimes are traversed: negligible diffusion of excitation among donors, diffusion-limited decay, and rapid diffusion.