The synthesis and structures of complex rare-earth halides

The interaction between two 4f electrons in a rare‐earth ion by means of the polarization of a ligand in a solid is discussed. It is shown that this interaction gives rise to a host dependent shift of the energy separations between the 4f N and 4f N−1 nl configurations. The results of the theory of these energy shifts are compared to experimental data for Nd3+, Er3+, and Tm3+ in the hosts YF3, LuF3, LiYF4, and LaF3. Also a shift in the Slater integrals and the spin–orbit parameter is predicted by the same interaction.

Host dependence of the rare‐earth ion energy separation 4f N–4f N−1 nl

Broad‐band vacuum ultraviolet (VUV) fluorescence has been observed in Nd3+‐, Er3+‐, and Tm3+‐doped LaF3, YF3, LiYF4, and LuF3 by electron‐beam and VUV excitation. The VUV excitation spectra indicate a large Stokes shift (≳5000 cm−1) and a high fluorescence quantum yield of 0.8. The threshold power for laser action in these crystals by optical pumping has been estimated. Using a molecular H2 laser as a pumping source, a laser system which is tunable from 1650 to 2600 A could be constructed.

C. Keller

Papers

Die Reaktion von Lithiumfluorid mit den Trifluoriden der Lanthaniden und einiger Actiniden