Abstract
The time dependence of the luminescence decay following pulsed excitation is examined for a system in which excited paramagnetic ions decay by a combination of intrinsic relaxation processes, direct energy transfer to acceptor ions, and energy migration. Three limiting cases are considered: direct energy transfer in the absence of diffusion, rapid diffusion, and diffusion-limited relaxation. Investigations of the transient europium fluorescence from a chromiumdoped europium phosphate glass, where excited ions form the donor system and impurities act as energy acceptors, are reported which illustrate these limiting cases. By varying the temperature and concentration, transient fluorescence behavior characteristic of diffusion-limited relaxation is studied. The data are analyzed to determine the probability for direct → energy transfer, the critical transfer distance for energy exchange, and the diffusion constant for energy migration through the europium system. varies with temperature as levels having greater probabilities for resonant - energy transfer become thermally populated. In the diffusion-limited relaxation case the decay rate is predicted to be proportional to ; this power law is verified.
- Received 30 April 1971
DOI:https://doi.org/10.1103/PhysRevB.4.2932
©1971 American Physical Society