Holmium ion

Johnson et al. (55) observed energy transfer from erbium to thulium and from erbium to holmium ions in crystals. They were able to obtain substantial decreases in laser thresholds because of this energy migration. The fluorescent lifetime of the 3//4 state of thulium in CaMo04 containing 0.75 atomic per cent erbium and 0.5 atomic per cent thulium as inferred from the time delay before the onset of laser oscillation is 900 /xsec at both IT and 20°K. 

In-line optical transmittance spectra of the Zr02-doped Ho Y203 ceramics sintered at 1800 °C for 30 h, which were from the powders corresponding to different slurry concentrations, are shown in Fig. 3.24. All the absorption peaks are related to holmium ion (Ho " ) absorption in the Y2O3 matrix. With decreasing slurry... 

The holmium ions order antiferromagnetically in the HoRu2Ge2 compound at the Neel temperature T = 20K. This compound exhibits a square modulated structure with a propagation vector k = (0.2216, 0.0111, 0) and a holmium magnetic moment of 6.6 parallel to the c-axis (Yakinthos and Roudaut 1987). 

Holmium is the 12th most abundant of the rare-earths found in the Earths crust. Although it is the 50th most abundant element on Earth, it is one of the least abundant lanthanide metals. It is found in gadolinite and the monazite sands of South Africa and Austraha and in the beach sands of Florida and the Carolinas in the United States. Monazite sand contains about a 50% mixture of the rare-earths, but only 0.05% by weight is holmium. Today, small quantities of holmium are produced by the ion-exchange process. 

Holmium is obtained from monazite, bastnasite and other rare-earth minerals as a by-product during recovery of dysprosium, thulium and other rare-earth metals. The recovery steps in production of all lanthanide elements are very similar. These involve breaking up ores by treatment with hot concentrated sulfuric acid or by caustic fusion separation of rare-earths by ion-exchange processes conversion to halide salts and reduction of the hahde(s) to metal (See Dysprosium, Gadolinium and Erbium). 

The radial dependence of the fluorescence-quenching interaction between terbium, holmium, and neodymium in aqueous chloride solution was examined by Holloway and Kestigian (108a). From the concentration dependencies of the fluorescence lifetimes, they concluded that the probability for quenching interaction falls off as 1/r6, where r is the average spacing between the ions. If the mechanism of resonance transfer is assumed, the observed radial dependence implies a dipole-dipole interaction. 

Oxalic acid is a precipitation agent for rare earth ions. The solubility of rare earth oxalates range from 10 to lO" mol in neutral solutions. The precipitate usually contains coordinated and/or lattice water molecules, RE2(C204)3 n H2O, where = 10 for lanthanum to erbium and yttrium while n = 6 for holmium, erbium, thulium, ytterbium to lutetium and scandium. 

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