OBSERVATION OF SHARP-LINE LANTHANIDE FLUORESCENCE IN HIGH-TEMPERATURE SUPERCONDUCTORS

Lanthanide fluorescence has been observed for the first time in the high temperature superconductors that have been recently discovered. Laser excited fluorescence and fluorescence excitation spectra of La//1//. //8//5// minus //xRE//xSr//0//. //1//5CuO//4 for RE equals Pr and Eu and x equals 0. 02, 0. 18, 0. 36 and 1. 85 are presented. There is substantial inhomogeneous broadening caused by the Sr**2** plus in the materials containing a single rare earth and additional broadening caused by the ionic size mismatch in the materials with two rare earths. The samples have 3 crystallographic sites for the lanthanide ion. No fluorescence was observed for the higher temperature superconductors, Y//1Ba//2Cu//3O//9// minus // delta , doped with 10 and 100% Eu**3** plus .