Mercury-like Ions Research Articles

Photoluminescent properties of Ca 2Gd 8(SiO 4) 6O 2: Dy 3+ phosphor films prepared by sol-gel process

There are growing interests on phosphor thin films owing to their potential application in high-resolution devices such as cathode ray tubes and flat panel display devices. The solution-based sol-gel method is one of the most important techniques for the synthesis of various functional coating films. Compounds with the apatite structure are very suitable host lattices for various luminescent ions. Ca 2RE 8(SiO 4) 6O 2 (RE=Y, Gd, La) is a kind of ternary rare-earth-metal silicate with oxyapatite structure, which has been used as host material for the luminescence of various rare earth and mercury-like ions. In this article, Ca 2Gd 8(SiO 4) 6O 2:Dy 3+ phosphor films were dip-coated on quartz glass substrates through the sol-gel process. X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL) spectra, as well as lifetimes were used to characterize the resulting films. AFM study revealed that the phosphor films consisted of homogeneous particles. The Dy 3+ showed its characteristic emission in crystalline phosphor films, i.e., 4F 9/2– 6H 15/2 and 4F 9/2– 6H 13/2.

Effect of halides on the electrochemiluminescence of heavy metals at an aluminum electrode

The effect of halides on cathodic electrochemiluminescence spectra of mercury-like ions at an aluminum electrode is studied. A method of changing the solution in concordance with the potential change is proposed to inhibit pitting corrosion arising in the anodic oxidation of aluminum in chloride-containing solutions. This method allows tin, lead, thallium, and mercury to be rapidly determined in model solutions and seawater.

Fabrication and Luminescence Properties of Ca 2Gd 8 (SiO 4) 6O 2: Er 3+ Phosphors via Sol-Gel Process

Ca 2RE 8(SiO 4) 6O 2(RE = Y, Gd, La) is a kind of ternary rare-earth-metal silicate with the oxyapatite structure, which was used as host materials for the luminescence of various rare earth and mercury-like ions. Ca 2Gd 8(SiO 4) 6O 2:Er 3+ phosphors were prepared through the sol-gel process. X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectra were used to characterize the resulting phosphors. The results of XRD indicate that the phosphors crystallized completely at 1000 °C. SEM study reveals that the average grain size is 400 ∼ 1000 nm. In Ca 2Gd 8 (SiO 4) 6O 2: Er 3+ shows its characteristic green emission at 528 nm ( 2H 11/2- 4I 15/2) and 548 nm ( 4S 3/2- 4I 15/2) upon excitation into 382 nm, with an optimum doping concentration of 5% (mole fraction) of Gd 3+ in the host lattices.

Quasirelativistic Hartree-Fock equations consistent with Breit-Pauli approach

The properties of the quasirelativistic Hartree-Fock equations are investigated. Different ways of forming the equations are discussed. The relativistic corrections employed in the traditional quasirelativistic Hartree-Fock equations are compared with the ones used within the Breit-Pauli approach. The two-electron contact interactions are revised and the new versions of the quasirelativistic Hartree-Fock equations are considered. The solutions of these equations are compared among themselves and also with those obtained within the Dirac-Fock and nonrelativistic Hartree-Fock approaches. Solution data are provided for some heliumlike, neonlike, and mercurylike ions.

Cathodic electrochemiluminescence of metal ions in acid fluoride solutions

The conditions for exciting the cathodic electrochemiluminescence (ECL) of mercury-like ions and manganese in dilute HF solutions at aluminum and magnesium electrodes are described. ECL spectra are measured. It is shown that Mn(II) can be determined with a detection limit of 10−7 M.

The luminescence of Eu3+ ion in Ca2Al2SiO7

Ca2Al2SiO7:Eu3+ was prepared by the sol–gel method. Through the emission spectrum of Eu3+ ion, the fluorescence parameters such as Ωi (i=2,4) and radiative transition probabilities of 5D0–7Fj were calculated. The Pb2+ ion with bigger radius has an effect on the fluorescence spectra of Eu3+ which can be explained by the structure of the matrix. Simultaneously, the energy transfers between mercury-like ions (Pb2+ and Bi3+) and Eu3+ ion were observed. The 5D4 and 5D2 energy levels of Eu3+ are the resonance ones for Pb2+ ion.

Electroluminescence of Mercury-like Ions on Aluminum Electrode

Experimental and theoretical aspects of electrochemical excitation of luminescence in mercury-like ions are considered. A technique intended for experimentally studying the luminescence kinetics in a flow cell is described. A model is proposed for the charge transfer and the excitation of mercury-like centers on an aluminum electrode. Effect of experimental parameters on the kinetic curves of radiation is considered. An equation that helps explain the observed regularities is suggested.

Scintillation characteristics of the single crystalline CdWO4 and Bi4Ge3O12 compounds doped with mercury-like ions

Scintillation characteristics of the single crystalline CdWO4 and Bi4Ge3O12 compounds doped with mercury-like ions

Characteristic luminescence of mercury and mercury-like ions at electrodes covered with insulating films

Intense electrogenerated luminescence of tin, indium and mercury at Al /Al2O3, Be/BeO, Mg/MgO and Mg/MgF2 electrodes was observed, and a mechanism of direct excitation of mercury-like centres by reduction with hot electrons was proposed.

Luminescence of mercurylike impurities in single-crystal CdWO4 compounds

The processes of crystallization by the method of liquid epitaxy are studied for the first time for single-crystal films of CdWO4 doped with the mercurylike ions Bi3+ and Pb2+, which can be used as thin-film components of combined scintillators for monitoring α- and β-activities. It is shown that in comparison with their solidcrystal analogs, the special features of these films consist in a longwave shift of the integral luminescence spectrum that is caused by high concentrations of the radiating complexes (VCd-WO6) with hvmax=2.05–2.15 eV and the “distorted” complexes (WO6)* in them. It is found that in the case of luminescence of single-crystal films CdWO4:Pb, radiation of mercurylike centers (PbO6) prevails with hvmax=2.87 eV, while in luminescence of CdWO4, radiation of centers (BiO6) with hvmax=2.16 eV and of complexes (VCd-WO6).

Luminescence and energy migration in the oxyapatite Ca2Gd8(SiO4)6O2 doped with several rare earth and mercury-like ions

Energy transfer phenomena have been observed by activating the oxyapatite host-lattice Ca2Gd8(SiO4)6O2 with Eu3+, Tb3+, Dy3+, Sm3+. This is based on the energy migration in the Gd3+ sublattice and trapping by the activators. The trapping efficiency for Gd3+ excitation energy increases in the sequence of Sm3+ < Dy3+ < Tb3+ < Eu3+. It is supposed that the activator ions are incorporated on both Gd3+ sites in Ca2Gd8(SiO4)6O2. The Gd3+ sublattice in Ca2Gd8(SiO4)6O2 can be sensitized by Pb2+ but not by Ce3+, Pr3+ and Bi3+.

Comment on "Relativistic excitation energies and oscillator strengths for the 6s2 1S0-->6s6p 1P1,3P1 transitions in Hg-like ions"

In a recent paper, Chou and Huang [Phys. Rev. A 45, 1403 (1992)] employ the multiconfiguration relativistic random-phase approximation (MCRRPA) in an attempt to remove discrepancies between experimental and theoretical oscillator strengths for the 6${\mathit{s}}^{2}$ $^{1}$${\mathit{S}}_{0}$\ensuremath{\rightarrow}6s6p $^{1}$${\mathit{P}}_{1}$, $^{3}$${\mathit{P}}_{1}$ transitions in mercurylike ions. Their MCRRPA results are found to be still in poor agreement with beam-foil measurements, and the authors suggest that a significant part of this disagreement may arise from ``an improper account of the cascade effects in beam-foil lifetime measurements.'' However, Chou and Huang have overlooked several, more recent beam-foil measurements in which ``proper'' account has been taken of cascading by the application of an arbitrarily-normalized-decay-curve technique with which their MCRRPA results are still in poor agreement. We conclude that this disagreement is mainly due to the omission by Chou and Huang from their calculation of core-polarization effects. In fact, calculations in which such effects are included show quite satisfactory agreement with the beam-foil measurements in which an account of cascade effects has been taken.

Mercury-like ions in glasses: Activators, sensitizers, stabilizers

Mercury-like ions in glasses: Activators, sensitizers, stabilizers

The luminescence of mercury-like ions alkaline earth sulfides

The luminescence of mercury-like ions in alkaline earth sulfides is reported, the results show that the luminescence spectra present certain regularity. In CaS two luminescent centers are observed for Pb 2+ and Bi 3+ ions respectively. Energy transfer phenomena from mercury-like ions or host lattice to Eu 2+ in MS are discussed.

The luminescence of mercury-like ions in and the crystal structure of SrLaBO 4

The crystal structure of SrLaBO 4 contains triangular borate groups. The luminescence of mercury-like ions (Sn 2+, Sb 3+, Tl +, Pb 2+, Bi 3+) in this host lattice is characterized by a large Stokes shift. The Pb 2+ is a very efficient activator at room temperature. The luminescent properties are discussed in terms of earlier models related to an off-center position of the metal ion. The emission of Eu 3+ shows that the crystal structure has a disordered nature and confirms an off-center position. Energy transfer from Pb 2+ to Eu 3+ and Tb 3+ was studied and found to be inefficient.

Photoionization cross sections of excited states of some mercury-like ions in alkali halide crystals

A method is proposed for determining the photoionization cross section of an excited state from the change in the relative quantum efficiency of intracenter luminescence. Measurements are reported of the cross sections of photoionization by intense radiation from an XeCl excimer laser of mercury-like Tl+, In+, and Sn2+ ions in alkali halide crystals.

Optical properties of Cs 2NaBiCl 6

Luminescence properties of Cs 2NaBiCl 6 are reported. Absorption, excitation, steady and pulsed fluorescence spectra have been investigated over a wide temperature range. The temperature dependences of the integrated fluorescence intensities and lifetimes versus temperature were obtained under selective excitation in the main absorption bands. Absorption processes are described using a molecular orbital scheme. The behaviour of the absorption (intensity and splitting) with the temperature provide evidence of a strong interaction with the lattice as shown in alkali halides doped with mercury-like ions. Emission processes are discussed. The lifetime measurements do not agree with the classical three-levels scheme generally proposed for luminescent processes in Bi 3+ centres. Absorption and emission results seem to support the hypothesis of a strong coupling with the vibrational modes. In addition, the behaviour of the decay times at low temperatures are consistent with migration and trapping sites effects.

Evolution du niveau 3P 1 des centres isoelectroniques du mercure en fonction de l'environnement

The authors show that the position of the 3P 1 level of the mercury-like ions (Tl +, Pb 2+, Bi 3+) depends on the difference between the ionic radii of the activator and the substituted cation. The corresponding curve presents a maximum or a minimum. The 3P 1 level of Bi 3+ centre is then studied in various compounds of La 3+ and Y 3+. The 3P 1 energy decreases when covalency increases in the rate earth-ligand bond.

Nature of the luminescence centers in ionic crystals

The main attention is paid to the following questions: 1. The possible models of the luminescence centers in activated alkali halide crystals, 2. the experimental evidence of the presence of various types of the luminescence centers, 3. the nature of the excitations of the simplest luminescence centers in alkali halides activated by mercury-like ions and by some other ions. Mainly two possibilities of views: the “quasi-free ions” case on the one hand and the “quasi-molecular” models on the other are discussed in detail.

On the "upper" and "lower" ionization of mercury-like ions in crystals of the KCl-Ga, Ag; KCl-In, Ag; and KCl-Tl, Ag types

On the "upper" and "lower" ionization of mercury-like ions in crystals of the KCl-Ga, Ag; KCl-In, Ag; and KCl-Tl, Ag types