FLUORESCENCE YIELDS OF ORGANIC LASER $MATERIALS^{*}$

$^{*}$Supported in part by Space Systems Division, Air Force Systems Command, Los Angeles, California. $^{1}$Weber, G., and F. W. J. Teale, Trans. Faraday Soc., 53, 646 (1957).Author Institution: Space Technology Laboratories, Inc.“The quantum yields of fluorescence of several rare-earth chelates have been measured as a function of concentration, solvent and temperature. Absolute yields were measured at room temperature using a technique described by Weber and $Teale^{1}$. Fluorescence intensities were measured over a range of temperature down to $77^{\circ} K$. Since the spectral distribution of fluorescence changes only slightly with temperature, quantum yields at Other temperatures may be obtained from the fluorescence intensity ratios. Of the compounds studied, europium tris benzoylacetonate, europium tris thienoyltrifluoroacetonate and terbium tris acetylacetonate appear to be especially favorable for optical maser applicatioins.