Energy Transfer in Silicate Glass Coactivated with Cerium and Ytterbium

• In a study of the optical properties of coactivated xuminescent glasses, CO c c r^ 2+ ^TJ3 + (1) J r ^,3+ XT,3+(2) , ^mr u ansfer of -nergy trom UO_ to Nd and troiTi Ce to Nd has been /-S 2 PMÜ observed and it has been shown that for both of these ion pairs this energ;' ^Jj^ lntcr(.■h>ln^^ is partly achieved by radiationless transfer mechanisms. In ^^ 3+ 3 + this paper the transfer of energy from Ce to Yb in a lithium-magnesiumalum-no silicate glass host matrix is reported and discussed. Direct evidence for energy transfer from Ce to Yb is given by a comparison of the excitation spectra for 1. OlSfi radiation in Figure 1. Inspection of these spectra clearly show the presence of a broad excitation band with a maximum around 0. 31fi in the coactivated glass (Figure IB) which is not present in this glass singly activated with ytterbium (Figure 1A). It is also shown that this gL ss singly activated with cerium does not give rise to 1. 015(j. radiation (Figure 1C). The 0. 31fi band is also an excitation band for the Ce ultraviolet emission, which is strong in the singly-activated glass, Mcasuremer-ts of the excitation spectra for Ce emission in these samples 3+ 3 + show that the reverse energy transfer, i. e. , Yb to Ce does not occur. 3+ 3 + The magnitude of the Ce to Yb transfer is indicated yy the observation that for the samples of the concentrations given in Figure 1, the Yb emission spectrum excited by 0. 313^ radiation (Ce absorption) is about 3+ 3 + twenty five times larger in the glass activated with Ce and Yb than in 3 + the glass activated with Yb alone. Using samples with 0. 01 cerium and 0. 02 ytterbium, a corresponding increase considerably greater than one hundred is observed. It is believed that the dominant mechanism of energy transfer is radiationless for two reasons: (1) a considerable shortening of the Ce" emission decay time is observed hi the coactivated glass, and (2) a strong 3 +