THE INFLUENCE OF NONRADIATIVE ENERGY-TRANSFER ON THE EXCITATION AND DECAY OF EXCITED-STATES OF ER3+ IN CS2NAERCL6

Evidence for efficient non-radiative energy transfer between erbium io ns in Cs2NaErCl6 is provided by excitation and luminescence spectra an d luminescence lifetimes. In one of the cross relaxation schemes the e xcitation of the 4F3/2 level is transferred almost exclusively to the 4F9/2 level in the 50-300 K temperature region. The process of cross r elaxation which removes the excitation from the 4S3/2 level is switche d thermally at about 100 K and attains high efficiency at room tempera ture. Experimental results are interpreted using previously reported e nergies of normal vibrations of ErCl(6)3- and the crystal-field levels of Cs2NaErCl6. It has been noted that virtually all efficient energy transfer schemes in Cs2NaLnCl6 reported thus far involve transitions b etween multiplets of the ground terms of lanthanides. All these transi tions obey the selection rules for magnetic dipole transitions.