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The electron absorption-, photoluminescence- and electron paramagnetic-resonance spectra of Mn3+ in red beryl from Wah Wah Mountains (Utah USA) and of pink- and purple vesuvianite from Jeffrey Mine (Asbestos, Canada) were measured at room- and low temperatures. The crystal field stabilization energies are equal to 130.9 kJ/mol for the red beryl, and 151.5-158.0 and 168.0 kJ/mol for for the pink- and the purple vesuvianite, respectively. The red photoluminescence of Mn3+ was not intensive either at room- or at low temperatures. The high Mn content in the crystals caused the emergence of an additional emission band and short photoluminescence-decay lifetimes. The latter are only 183 μs for beryl and 17 μs for vesuvianite. [ABSTRACT FROM AUTHOR]

A series of the Tb- and Dy-doped glasses with Li2O--2B2O3 (or Li2B4O7:Tb and Li2B4O7:Dy) composition were synthesised and their spectroscopic properties were investigated. The Li2B4O7:Tb and Li2B4O7:Dy glasses of high chemical purity and optical quality were obtained from corresponding polycrystalline compounds in the air using standard glass technology. The Tb and Dy impurities were added to Li2B4O7 composition in the form of Tb2O3 and Dy2O3 oxide compounds in amounts of 0.5 and 1.0 mol%. The electron paramagnetic resonance (EPR), luminescence excitation and emission spectra of the Li2B4O7:Tb and Li2B4O7:Dy glasses were investigated. On the basis of EPR and photoluminescence spectra analysis it was shown that the Tb and Dy impurities are incorporated in the Li2B4O7 glass network as Tb3+ (4f8, 7F6) and Dy3+ (4f 9, 6H15/2) ions, exclusively. All observed transitions of the Tb3+ and Dy3+ centres in the luminescence excitation and emission spectra were identified. The luminescence kinetics shows single exponential decay for Tb3+ and Dy3+ centres in Li2B4O7 glasses. The lifetime values for main emission transitions of the Tb3+ and Dy3+ centres in the Li2B4O7 glasses containing 0.5 and 1.0 mol% Tb2O3 and Dy2O3 are determined at T = 300 K. Peculiarities of optical properties and local structure of the Tb3+ and Dy3+ centres in the Li2B4O7:Tb and Li2B4O7:Dy glasses as well as their potential applications have been discussed. [ABSTRACT FROM AUTHOR]

Optical absorption, luminescence excitation, and emission spectra as well as luminescence kinetics of the Sm- and Yb-doped glasses with lithium tetraborate (Li2B4O7) composition were investigated and analysed. The Sm- and Yb-doped lithium tetraborate glasses of high optical quality were obtained in air from corresponding polycrystalline compounds according to standard glass synthesis technology. The Sm and Yb impurities were added to the Li2B4O7 compound in the form of Sm2O3 and Yb2O3 oxides in amount of 0.4 mol%. Using optical and electron paramagnetic resonance spectroscopy it was shown that the Sm and Yb impurities are incorporated into the lithium tetraborate glass network as Sm3+ (4f5, 6H5/2) and Yb3+ (4f13, 2F7/2) ions, exclusively. All of the observed transitions in the absorption and luminescence spectra of Sm3+ and Yb3+ centres were identified. The luminescence kinetics of the Sm3+ and Yb3+ centres in the Li2B4O7 glass are characterised by a single exponential decay. Decay constants for the main emission transitions of the Sm3+ and Yb3+ centres in the lithium tetraborate glass were obtained at T = 300 K. Incorporation peculiarities and optical spectra of Sm3+ and Yb3+ ions in the lithium tetraborate glass have been discussed in comparison with other borate glasses and crystals. [ABSTRACT FROM AUTHOR]

Optical absorption and luminescence spectra as well as luminescence kinetics of the Nd3+ centres in glasses with Ca3Ga2Ge3O12:Nd composition, containing 0.2 and 1.0 wt% of the Nd2O3 were presented and analysed. The oscillator strengths and phenomenological intensity parameters Ωt (Ω2, Ω4, and Ω6) were obtained using standard Judd-Ofelt theory. Calculated Ωt parameters, radiative transitions rates, branching ratios and radiative lifetime for Nd3+ centres in the glass with Ca3Ga2Ge3O12 composition were analysed and compared with corresponding Nd3+ parameters in their crystalline analogue with garnet structure. Experimental lifetimes are compared with those calculated, and quantum efficiency of Nd3+ centres from 4F3/2 emitting level in the glass with Ca3Ga2Ge3O12 composition is estimated. Incorporation peculiarities and local structure of Nd3+ luminescence centres in the glass with Ca3Ga2Ge3O12 composition and corresponding Ca3Ga2Ge3O12:Nd3+ garnet laser crystals are considered. On the basis of extended X-ray absorption fine structure (EXAFS) spectra (L3-edge) of rare-earth elements analysis it has been shown that Nd3+ luminescence centres in the CaO-Ga2O3-GeO2 glass network occupy structural sites with the coordination number to oxygen N = 6. [ABSTRACT FROM AUTHOR]

The color change of the pink and colorless LiAlSi2O6 spodumene crystal due to irradiation and heating is explained. The hypothesis about the change of Mn3+ to Mn4+ after irradiation was rejected. For the studied crystals, it was shown that both Mn2+ and Mn3+ occupy the M2 (not the M1) crystal site. Spodumene crystals which are primary pink (kunzite) contain Mn3+ (and Mn2+) at the M1 site. By contrast, those that become pink due to irradiation and heating contain Mn3+ and Mn2+ at the M2 site. The emission band of the former is 625 nm, and for the latter, it is 591 nm. [ABSTRACT FROM AUTHOR]

Spectroscopic and luminescent properties of the Pr-doped and Pr–Ag co-doped borate glasses with Li 2 B 4 O 7 (Li 2 O–2B 2 O 3) composition are studied and discussed. Experimental and theoretical oscillator strengths (f exp and f theor), phenomenological parameters (Ω 2 , Ω 4 , Ω 6), radiative properties (A rad , β , τ rad), and quantum efficiencies (η) of the Pr3+ luminescence were calculated basing on the obtained experimental results and Judd–Ofelt theory. Most intense band of the Pr3+ luminescence is peaked at 601 nm (1D 2 → 3H 4 transition). Presence of the isolated Ag+ (4 d 10, 1S 0) ions, small non-plasmonic Ag aggregates (Ag m n + nanoclusters), and plasmonic Ag metallic nanoparticles in the Li 2 B 4 O 7 :Pr,Ag glass was proposed basing on analysis of the photoluminescence and optical absorption spectra. Observed enhancement of luminescence intensity and increasing of stimulated emission cross-section and quantum efficiency of luminescence in the Li 2 B 4 O 7 :Pr,Ag glass is explained by energy transfer from Ag species to the Pr3+ ions as wells local-field effect induced by Ag nanoparticles. • The Pr-doped and Pr–Ag co-doped Li 2 B 4 O 7 glasses of high optical quality were obtained. • Optical absorption, EPR, photoluminescence spectra and decay kinetics were studied. • Judd-Ofelt parameters (Ω 2 , Ω 4 , Ω 6) and radiative properties (A rad , β , τ rad , σ em , η) were calculated. • Enhancement of the Pr3+ emission intensity in the Li 2 B 4 O 7 :Pr,Ag glass was observed. • Mechanisms of the Pr3+ luminescence improvement in the Li 2 B 4 O 7 :Pr,Ag glass is proposed. [ABSTRACT FROM AUTHOR]

Spectroscopic and luminescent properties of the Nd-doped and Nd–Ag co-doped borate glasses with Li 2 B 4 O 7 (Li 2 O–2B 2 O 3) basic composition are investigated and analysed using optical absorption, electron paramagnetic resonance (EPR), photoluminescence (excitation, emission, decay kinetics) experimental methods and Judd–Ofelt analysis. Optical absorption, photoluminescence spectra and decay kinetics of Nd3+ ions were registered and detailed analysed. Experimental and theoretical oscillator strengths (f exp and f theor), Judd–Ofelt intensity parameters (Ω 2 , Ω 4 , Ω 6), and important to laser applications radiative parameters such as probabilities of radiative transitions (A rad), branching ratios of luminescence (β), radiative lifetimes (τ rad), emission cross-sections (σ em), and quantum efficiency (η) of the Nd3+ luminescence in the Li 2 B 4 O 7 :Nd and Li 2 B 4 O 7 :Nd,Ag glasses have been calculated. Broad absorption band of surface plasmon resonance (SPR) related to silver nanoparticles was observed in the Li 2 B 4 O 7 :Nd,Ag glass. Presence of the Ag paramagnetic centres and aggregates in the Li 2 B 4 O 7 :Nd,Ag glass was confirmed by EPR spectroscopy. Photoluminescence emission and excitation spectra as well as decay kinetics of the Ag+ ions and small non-plasmonic Ag aggregates or nanoclusters were registered and discussed. Observed enhancement of the Nd3+ luminescence intensity in the Li 2 B 4 O 7 :Nd,Ag glass is explained by effects induced by SPR of the Ag nanoparticles as wells energy transfer from Ag+ ions and Ag aggregates to the Nd3+ ions. Image 1 • The Nd-doped and Nd–Ag co-doped Li 2 B 4 O 7 glasses of high optical quality were obtained. • Optical absorption, EPR, photoluminescence spectra and decay kinetics were studied. • Judd-Ofelt parameters (Ω 2 , Ω 4 , Ω 6) and radiative properties (A rad , β , τ rad , σ em , η) were calculated. • Enhancement of the Nd3+ luminescence in the Li 2 B 4 O 7 :Nd, Ag glass was obtained. • Silver co-doping improves luminescent and laser properties of the Nd3+-doped borate glasses. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of Pb-containing glasses of high optical quality and chemical purity are obtained. • XRD, IR transmission, UV-Vis absorption & photoluminescence of obtained glasses are studied. • Intrinsic photoluminescence broad bands in the visible range were discovered and analysed. • Fast and slow recombination mechanisms for intrinsic photoluminescence bands were proposed. • The studied glasses are perspective luminescent materials of the visible spectral range. The X-ray diffraction, infrared transmission, optical absorption, photoluminescence spectra and decay kinetics of a series of un-doped Pb-containing glasses with compositions of 0.4PbO–0.6GeO 2 , 0.6PbO–0.4SiO 2 , 0.7PbO–0.3B 2 O 3 , and 0.54PbO–0.34B 2 O 3 –0.12GeO 2 were studied. Average interatomic distances and coordination numbers for main structural units GeO 4 , SiO 4 , BO 4 , BO 3 , and PbO n (n = 3 – 6) in all studied glasses were derived from radial distribution functions. The 0.4PbO–0.6GeO 2 and 0.54PbO–0.34B 2 O 3 –0.12GeO 2 glasses upon UV photoexcitation show intense broad emission bands with maxima at 478 and 543 nm, respectively, and weaker broad band with peak about 610 nm. Based on luminescence decay kinetics analysis were proposed fast (band-to-band recombination) and slow (recombination with participation of point defects) mechanisms of intrinsic luminescence in the 0.4PbO–0.6GeO 2 and 0.54PbO–0.34B 2 O 3 –0.12GeO 2 glasses. The 0.6PbO–0.4SiO 2 and 0.7PbO–0.3B 2 O 3 glasses under UV – violet photoexcitation reveal only broad emission band with a maximum at 599 and 593 nm, respectively, caused by the band-to-band fast recombination mechanism. [ABSTRACT FROM AUTHOR]