Energy Migration Processes in Rare Earth Pentaphosphates.

Scope and Method of Study. A review of the theoretical approaches to the energy migration processes was made. A Time-resolved site-selection technique was used to study spectral energy migration between Eu('3+) ions in Eu(,x)Y(,1 -x)P(,5)O(,14). A Four-wave mixing technique was used to investigate energy migration in Nd(,x)La(,1-x)P(,5)O(,14). Findings and Conclusions. It was concluded that the current progress in the theory of energy migration presents the approximate description of the energy migration through averaged, discrete medium with low concentration of the optical active ions. In EuP(,5)O(,14) the energy transfer was found to be of Forster-Dexter type. At the same time in Eu(,0.01)Y(,0.99)P(,5)O(,14) energy transfer dynamics indicates the possibility of the aggregation of Eu('3+) ions. Energy transfer was found to be temperature independent. In Nd(,x)La(,1-x)P(,5)O(,14) the energy migration process was found to be dependent on dopant concentration, temperature, excitation wavelength and excitation power. In Nd(,0.2)La(,0.8)P(,5)O(,14) excitons show partially coherent, diffusive behaviour. In NdP(,5)O(,14) departure from the diffusive behaviour of excitons was observed. The process of ion-phonon interaction was found to be limiting the degree of coherence in the exciton motion.