Study on the energy transfer processes in rare-earth pentaphosphate crystals

Time evolUtions of the sup(4)Fsub(3/2)Ndsup(3+) metastable level population in Lasub(1-x-y)Ndsub(x)Lnsub(y)Psub(5)OsUb(14) (Ln-Tb, Eu) crystals in a wide series of donor and acceptor concentrations are studied. Radiationless energy transfer from the 5D0 state of Eu3+ ions to Nd3+ ions is observed. The accurate radiationless loss function for statical energy transfer in neodymium pentaphosphate is calculated and with its help multipolarity and microparameters of Nd-Ln (Ln-Tb, Eu) donor-acceptor interaction are determined. It is found that when increasing the donar concentration their luminescence quenching starts in the kinetic limit mode. It is shown that at the studied donor concentrations the migration-accelerated quenching is not described by the well-known jump mechanism formulae and adequate description is provided by the more accurate formula considering the crystal structure that is true at any relation between the quenching sphere radius and minimum donor-acceptor distance. Using different Nd3+ ion luminescence quenchers the value of Csub(DD) (Nd-Nd) microparameter describing the process of excitation transport in pentaphosphate crystals is found. Correspondence betWeen experimental and calculated critical donor concentrations when exceeding which donor luminescence quenching proceeds in the kinetic limit mode is found