Time- and Temperature-Dependent Luminescence of Manganese Ions in Ceramic Magnesium Aluminum Spinels.

Samples of magnesium aluminum spinel ceramics doped with manganese ions were prepared by a high-temperature solid-state reaction method; their potential as red-emitting phosphors was analyzed using a time-resolved luminescence spectroscopy technique, from room temperature to 10 K. It was found that in the red spectral range, the luminescence spectra of manganese ions in the MgAlO spinel showed a narrow band peaking at 651 nm due to the emission of Mn and a broader emission band in the region of 675 ÷ 720 nm; the ratio of intensities for these bands depends on the synthesis conditions. By applying a special multi-step annealing procedure, the MgAlO:Mn phosphor containing only tetravalent manganese ions, Mn, was synthesized.

"A bridge over troubled gaps": up-conversion driven photocatalysis for hydrogen generation and pollutant degradation by near-infrared excitation.

Spectral up-conversion (UC) has been attracting growing interest for the effective harvesting of the near-infrared (NIR) part of sunlight for photocatalytic hydrogen production and environmental purification. We present evidence of NIR-to-UV-VIS photon conversion for degradation of organic dyes and hydrogen and oxygen evolution via water-splitting by TiO and Rh-Cr oxide-loaded SrTiO:Al photocatalysts, respectively.

Emission and excitation spectra of Ce3+ and Pr3+ ions in hexafluoroelpasolite lattices.

The emission and excitation spectra of Ce(3+) and Pr(3+) doped into the cubic host Cs(2)NaYF(6) have been recorded at room temperature and ∼10 K using synchrotron radiation. The two 5d(1) T(2g) states of Ce(3+) have been located from the excitation spectra, whereas the E(g) state is placed above the host band gap. Decay measurements of the 5d(1) → 4f(1) Ce(3+) emission, and spectra collected using selective excitation, indicate the occupation of more than one type of site by Ce(3+) in this host lattice.

Vacuum ultraviolet excitation spectra of lanthanide-doped hexafluoroelpasolites.

Vacuum ultraviolet excitation spectra at ∼10 K have been recorded for [Formula: see text] transitions of Cs(2)NaYF(6):Ln(3+) (Ln = Nd, Sm, Eu, Tb, Ho, Er, Tm). In these high bandgap hosts the lanthanide ions occupy octahedral symmetry sites. The spectra comprise broad, structured bands and in most cases the individual vibronic structure is not resolved.

EPR, ENDOR and HYSCORE study of X-ray induced centres in K2YF5 thermoluminescent phosphors.

X-Ray irradiation at room temperature produces several paramagnetic centres in rare-earth activated K2YF5 crystals, whose thermal annealing behaviour can be linked with the occurrence of thermoluminescence (TL) glow peaks. In this paper, continuous wave (CW) and pulsed paramagnetic resonance techniques are used to study the structure of a very stable radiation-induced centre, which may be involved in the TL peak at approximately 390 degrees C reported for Ce- and Tb-activated crystals. From the spectra the centre's g tensor and hyperfine (nuclear quadrupole) tensors for several 19F and 39K neighbouring nuclei are extracted, but no self-hyperfine interaction could be detected.

EPR and ENDOR analysis of Fe3+ impurity centers in fluoroelpasolite lattices.

Fe(3+) ions in hexagonal and cubic fluoroelpasolite crystals (A(1)(2)B(I)M(III)F(6)) have been investigated in a combined Electron Paramagnetic Resonance (EPR) and Electron Nuclear Double Resonance (ENDOR) study. A detailed analysis of the ENDOR spectra for the nearest (19)F and (23)Na shells in X (9.5 GHz) and Q band (34 GHz) allowed the complex EPR spectra to be disentangled and to determine the spin Hamiltonian parameters for the various S = 5/2 Fe(3+) centres.

Inter- and intraconfigurational transitions of Nd3+ in hexafluoroelpasolite lattices.

Excitation of the 4f3 ion Nd3+ in hexafluoroelpasolite lattices by synchrotron radiation of wavelength approximately 185 nm leads to fast 4f(2)5d --> 4f3 emission below 52,630 cm(-1) and slower 4f3 --> 4f3 emission from the luminescent states (4)F(3/2) gamma8u (11 524 cm(-1)) and 2G2(9/2) gamma8u (approximately 47,500 cm(-1)). The near-infrared emission is well-resolved, and a clear interpretation of the 4I(9/2) crystal field levels and of the one-phonon vibronic sideband is given. The excitation spectrum of the 2G2(9/2) emission enables clarification of the structure of the 4f(2)5d configuration (which extends from approximately 52,000 to 128,000 cm(-1)).

Thermoluminescence response of K2YF5:Tb3+ crystals to photon radiation fields.

This investigation has been performed to test the feasibility of using K2YF5:Tb3+ crystals as thermoluminescence dosemeters (TLD). K2YF5 single crystals doped with 0.2, 10.

Thermoluminescent characteristics of LiKYF5:Pr3+ and KYF4:Tm3 crystals for applications in neutron and gamma dosimetry.

Thermoluminescent (TL) properties of two concentration series lithium potassium yttrium fluoride doped with praseodymium (LiKYF5:Pr3+) and potassium yttrium fluoride doped with thulium (KYF4:Tm3+) have been investigated after gamma and neutron irradiation. The main purpose of this research is to see whether these materials are suitable for gamma and/or neutron dosimetry purposes. It has been found that the compounds of both series are sensitive to 60Co gamma radiation.

Luminescence of CsGd2F7 crystals.

Optical and dosimetric properties of nominally pure CsGd2F7 crystals and of CsGd2F7 crystals doped with various concentrations of Pr3+ ions were investigated. Effects of X, beta and UV irradiation on these crystals were studied. Methods of optical absorption, X and UV excited luminescence, thermoluminescence (TL), phototransferred thermoluminescence and optically stimulated luminescence were used in these investigations.

Spectroscopy and stimulated emission of Nd(3+) in an acentric CsY(2)F(7) host.

The results of preliminary spectroscopic studies of new fluoride single-crystal CsY(2)F(7) that is activated by Nd(3+) ions are given. Direct evidence for the possibility of application of this ordered material as a laser host is given for the first time to our knowledge. Stimulated emission of Nd(3+) ions on the main intermultiplet transition is obtained under both nonselective flash-lamp pumping conditions and continuous Ar ion laser pumping conditions.