Far infrared spectral lines and absorptance calculation of NO

The positions and intensities of pure rotation lines of ¹⁴N¹⁶O have been calculated between 10–200 cm^-1 and are tabulated. The line by line absorption spectrum has been computed using tabulated parameters, and compared with experimental spectra measured by other authors. The spectral emission of atmospheric NO has been calculated for an altitude of 14.5 km, where some measurements have been carried out. After comparing the NO and the background H₂O+O₂+O₃ spectra, it is shown that the NO emission in the far i.r. spectrum of the lower stratosphere is negligible.     

Eu activated M6AlP5O20 (M=Sr/Ba/Mg) novel red phosphors

Eu³⁺ activated M₆AlP₅O₂₀ (where M=Sr/Ba/Mg) phosphors prepared by combustion synthesis and the completion of the synthesis was confirm by XRD (X-ray diffraction) patterns. The surface morphology studied by scanning electron microscopy (SEM) and photoluminescence (PL) properties has been reported in this paper. The Eu³⁺ PL emission spectrum was observed in M₆AlP₅O₂₀ phosphors (where M=Sr/Ba/Mg) at 592 (orange) and 618 nm (red) region, the spectrum due to ⁵D₀→⁷F₁ and ⁵D₀→⁷F₂ transitions at mercury free excitation, respectively. Its considerable emission intensity under 350 nm excitations makes it possible candidate materials as red component of tricolor luminescence materials and for near ultra violet light emitting diode (n-UVLED) phosphors.     

Effective energy transfer between Ceand Eu in CaAl2Si2O8 host under vacuum ultraviolet illumination

We presented the energy transfer from Ce³⁺ to Eu²⁺ in CaAl₂Si₂O₈ host. The Ce³⁺-doped CaAl₂Si₂O₈ phosphor had a strong emission band at 378 nm under the vacuum ultraviolet (VUV) light. This emission spectrum of Ce³⁺ well overlapped with the excitation spectrum of Eu²⁺ under the UV illumination. As a result, the energy transfer from Ce³⁺ to Eu²⁺ in CaAl₂Si₂O₈ matrix was observed under VUV excitation, which resulted in a significant enhancement of the emission peak intensity at 446 nm. More details about the luminescent properties were presented.     

Ca2SiO4:Dy3+材料的制备及其发光特性

采用高温固相法制备了Ca₂SiO₄:Dy³⁺发光材料.在365nm紫外光激发下,测得Ca₂SiO₄:Dy³⁺材料的发射光谱为一多峰宽谱,主峰分别位于486nm,575nm和665nm处;监测575nm发射峰,测得材料的激发光谱为一多峰宽谱,主峰分别位于331nm,361nm,371nm,397nm,435nm,461nm和478nm处.研究了Dy³⁺掺杂浓度对Ca₂SiO₄:Dy³⁺材料发射光谱及发光强度的影响,结果显示,随Dy³⁺浓度的增大,黄、蓝发射峰强度比(Y/B)逐渐增大,利用Judd-Ofelt理论解释了其原因;随Dy³⁺浓度的增大,Ca₂SiO₄:Dy³⁺材料发光强度先增大,在Dy³⁺浓度为4 mol%时到达峰值,而后减小,根据Dexter理论其浓度猝灭机理为电偶极-电偶极相互作用.研究了电荷补偿剂Li⁺,Na⁺和K⁺对Ca₂SiO₄:Dy³⁺材料发射光谱的影响,结果显示,不同电荷补偿剂下,随电荷补偿剂掺杂浓度的增大,Ca₂SiO₄:Dy³⁺材料发射光谱强度的演化趋势相同,即Ca₂SiO₄:Dy³⁺材料发射峰强度先增大后减小,但不同电荷补偿剂下,材料发射峰强度最大处对应的补偿剂浓度不同,对应Li⁺,Na⁺和K⁺时,浓度分别为4mol%,4mol%和3mol%. 关键词： 白光LED 2SiO₄:Dy³⁺')" href="#">Ca₂SiO₄:Dy³⁺ 发光特性 电荷补偿     

Observations of 63 μm atomic oxygen emission in the earth's atmosphere from balloon altitudes: Astronomical implications

Measurements of ³P₁ → ³P₂ 63 μm atomic oxygen (OI) emission in the earth's atmosphere obtained with a balloon-borne telescope and high-resolution Fourier transform spectrometer are presented. Three results emerge from analysis of this data: (i) the frequency of the OI ³P₁ → ³P₂ transition was determined to be 158.2693 ± 0.003 cm⁻¹; (ii) the integrated line intensity of the atmospheric OI emission was determined to be 2.4 ± 0.5 · 10⁻⁵ W m⁻² sr⁻¹; and (iii) the integrated line intensity of the atmospheric OI emission was found to be constant over a range of zenith angles corresponding to air-mass values between 1.27 and > 20. The implications of these results on astronomical observations of OI emission are discussed.     

Diagnosis of OH radical by optical emission spectroscopy in a wire-plate bi-directional pulsed corona discharge

The emission spectrum of the molecule OH (A²Σ→X²Π, 0–0) during a high-voltage, bi-directional pulsed corona discharge consisting of a gas mixture of N₂ and H₂O in a wire-plate reactor has been successfully recorded under severe electromagnetic interference at atmospheric pressure. The relative vibrational populations and the vibrational temperature of N₂ (C, v′) have also been determined. Due to the difficulty of determining the exact overlapping spectral line shape function of the OH (A²Σ→X²Π, 0–0) and the Δv=+1 vibrational transition band of N₂ (C³Π_u→B³Π_g), a practicable Gaussian form is used for calculating the emission intensity of OH (A²Σ→X²Π, 0-0) and the Δv=+1 vibrational transition band of N₂ (C³Π_u→B³Π_g). The emission intensity of OH (A²Σ→X²Π, 0–0) has been evaluated with a satisfactory accuracy by subtracting the emission intensity of the Δv=+1 vibrational transition band of N₂ (C³Π_u→B³Π_g) from the overlapping spectra. The relative population of OH (A²Σ) has been obtained by the emission intensity of OH (A²Σ→X²Π, 0–0) and Einstein's transition probability. The influences of peak voltage, pulse repetition rate and O₂ flow rate on the relative population of OH (A²Σ) radicals have also been investigated. We found that the relative population of OH (A²Σ) rises with an increase in both the peak applied voltage and the pulse repetition rate. When oxygen is added to an N₂ and H₂O gas mixture, the relative population of OH (A²Σ) radicals decreases exponentially with an increase in added oxygen. The main physicochemical processes involved are also discussed in this paper.     

Single-phased silicate-hosted phosphor with 660 nm-featured band emission for biological light-emitting diodes

A single-phased (Ba,Sr)₃MgSi₂O₈:Eu²⁺, Mn²⁺ phosphor with 660 nm-featured dual band-emission is investigated upon optimizing composition to simulate the artificial photosynthetic action spectrum (PAS) for near-ultraviolet (NUV) biological light-emitting diodes (bio-LEDs). A specific composition range in Ba–Sr binary solid solution of (Ba,Sr)₃MgSi₂O₈ is found to be capable of obtaining single-phased host in the absence of an easily formed orthosilicate impurity, leading to a 660 nm-featured red band emission of Mn²⁺ induced by an efficient energy transfer from a co-doped blue-emitting Eu²⁺ sensitizer. This dual broad band emission phosphor has a 72 nm full width at half maximum (FWHM) for red band that covers fairly well to the absorption spectrum of chlorophyll and PAS for most plants, enabling a flexible option in the application of bio-illumination for artificial photosynthesis.     

Spectroscopic properties of OH doped and Bi-rich Bi4Ge3O12 crystals by vertical Bridgman method

OH⁻ doped and Bi-rich Bi₄Ge₃O₁₂ (BGO) single crystals were grown by Vertical Bridgman (VB) method. The structure of these crystals was determined by XRD, and the emission spectra in visible and near infrared region (NIR) were measured at room temperature. The emission spectrum of Bi-rich BGO has extra peaks at 385, 367 and 357 nm, Bi-rich BGO after annealing in Ar at 500 °C for 5 h shows a significant emission band peaking around 1170 nm under 808 nm laser diodes (LDs) excitation, and OH⁻ doped BGO shows a noticeable emission band centered at about 1346 nm under 980 nm LDs excitation. A brief discussion is presented.     

Effect of SiO2/Si3N4 dielectric distributed Bragg reflectors (DDBRs) for Alq3/NPB thin-film resonant cavity organic light emitting diodes

In this article, we report on the effect of SiO₂/Si₃N₄ dielectric distributed Bragg reflectors (DDBRs) for Alq₃/NPB thin-film resonant cavity organic light emitting diode (RCOLED) in increasing the light output intensity and reducing the linewidth of spontaneous emission spectrum. The optimum DDBR number is found as 3 pairs. The device performance will be bad by further increasing or decreasing the number of DDBR. As compared to the conventional Alq₃/NPB thin-film organic light emitting diode (OLED), the Alq₃/NPB thin-film RCOLED with 3-pair DDBRs has the superior electrical and optical characteristics including a forward voltage of 6 V, a current efficiency of 3.4 cd/A, a luminance of 2715 cd/m² under the injection current density of 1000 A/m², and a full width at half maximum (FWHM) of 12 nm for emission spectrum over the 5-9 V bias range. These results represent that the Alq₃/NPB thin-film OLED with DDBRs shows a potential as the light source for plastic optical fiber (POF) communication system.     

Excited state dynamics and energy transfer rates in Sr3Tb0.90Eu0.10(PO4)3

The emission spectrum of neat Sr₃Tb(PO₄)₃ upon excitation at 337 nm in the levels above ⁵D₃ is dominated by ⁵D₄ emission and no significant emission from ⁵D₃ is observed due to efficient cross relaxation involving the Tb³⁺ levels. On the other hand, the emission spectrum of the same host containing 10 mol% Eu³⁺ upon excitation at the same wavelength (in the Tb³⁺ levels) is dominated by strong emission bands from the ⁵D₀ level of Eu³⁺. This clearly indicates that Tb³⁺→Eu³⁺ energy transfer is present. The excitation spectrum of the Eu^{3+ 5}D₀ emission is dominated by Tb³⁺ bands extending in the UV region.The presence of 10 mol% Eu³⁺ in Sr₃Tb(PO₄)₃ very strongly shortens the ⁵D₄ decay time. The decay curve is not far from exponential, indicating that the energy transfer to Eu³⁺ is accompanied by fast energy migration. The transfer regimes are identified and the donor–donor and donor–acceptor transfer microparameters are quantified under the assumption of electric dipole–electric dipole interactions.     

Photoluminescence properties of Eu in lithium titanate

Lithium titanate ceramics doped with Eu were synthesized and their photoluminescence (PL) and emission spectral characteristics were investigated. PL spectra of the sample showed peaks corresponding to the ⁵D₀→⁷F_J (J=0, 1, 2, 3 and 4) transitions under 230 nm excitation. The fluorescence lifetimes of Eu³⁺ ions were found out to be 645 μs. Strong red emission coming from the hypersensitive ⁵D₀→⁷F₂ transition of Eu³⁺ ion suggested the presence of the dopant ion in highly asymmetric environment. Further analysis of the emission spectrum revealed that the symmetry of the metal ion is very low i.e. C₂. The emission intensity of the sample was compared with a commercial phosphor to get an idea about the commercial utility of the phosphor. Various emission properties for the system namely Judd-Ofelt intensity parameters, spontaneous emission probabilities, branching ratios, radiative lifetimes and quantum efficiency were evaluated for the dopant ion by adopting standard procedure.     

Magnetic resonance in Ge0.99Mn0.01 nanowires

The contributions of several different subsystems to the magnetic properties of Ge_0.99Mn_0.01 nanowires are distinguished. The ferromagnetic resonance spectrum is found to have four components, two of which have the same temperature dependence and a Lorentzian shape. Presumably, these components correspond to the excitation of spin waves in the Mn³⁺ ion subsystem under the simultaneous influence of exchange and dipole-dipole interactions. There is also another Lorentzian-shaped component corresponding to resonance in the subsystem of localized Mn²⁺ centers. The fourth spectrum component has an asymmetric Dyson shape and is related to the resonance of mobile paramagnetic centers. A correlation is found between the temperature dependences of the spectral parameters of the magnetic resonances of the localized centers (Mn³⁺ and Mn²⁺ ions) and the charge carrier subsystem. This correlation indicates that the ferromagnetic exchange between the localized centers is due to carrier spin transport.     

Luminescence characteristics of Eu3+ activated borate phosphor for white light emitting diode

In this paper, the Sr₃Y₂ (BO₃)₄:Eu³⁺ phosphor was synthesized by high temperature solid-state reaction method and the luminescence characteristics were investigated. The emission spectrum exhibits one strong red emission at 613nm corresponding to the electric dipole ⁵D₀--⁷F₂ transition of Eu³⁺ under 365nm excitation, this is because Eu³⁺ substituted for Y³⁺ occupied the non-centrosymmetric position in the crystal structure of Sr₃Y₂ (BO₃)₄. The excitation spectrum indicates that the phosphor can be effectively excited by ultraviolet (254nm, 365nm and 400nm) and blue (470nm) light. The effect of Eu³⁺ concentration on the red emission of Sr₃Y₂ (BO₃)₄:Eu³⁺ was measured, the result shows that the emission intensities increase with increasing Eu³⁺ concentration, then decrease. The Commission Internationale del'Eclairage chromaticity (x, y) of Sr₃Y₂(BO₃)₄:Eu³⁺ phosphor is (0.640,0.355) at 15 mol% Eu³⁺.     

Radioluminescent mechanism of Li2B4O7:Cu crystal

The structure of the radioluminescent (RL) spectrum of Li₂B₄O₇:Cu crystal is complex, having no normal Gauss peaks. The RL spectrum recorded showed one sharp and strong peak near 365 nm. For the purpose of explaining this phenomenon, we used the self-trapped exciton (STE) model to analyze experimental data of absorption spectrum, emission spectrum, radioluminescence spectrum and decay-time curves. We found a short lifetime component (of the order of ns) from phosphorous signals of Li₂B₄O₇:Cu. We realized that the short lifetime component related to inherent signal of host lattice and the d-p transitions of Cu⁺. This result is applicable in the detector system with high time resolution.     

Synthesis, characterization and fluorescence studies of a novel europium complex based sensor

A novel europium(III) complex was synthesized using TTA (α-thenoyltrifluoroacetone) as the first ligand and H₂bpdc (2,2′-bipyridine-3,3′-dicarboxylate) as the second ligand. Elemental analysis, thermal analysis, IR and UV–vis spectrum and fluorescence spectrum of the europium(III) complex were carried out. A characteristic Eu³⁺ fluorescence emission was observed in ethanol–water (1:1) solution, indicating that the complex is stable in solution and the emission of Eu(III) ions was not influenced by the water molecules. The fluorescence emission of the complex was quenched completely by the Co²⁺ and Fe³⁺ ions, but the quenched emission was recovered in the presence of glycine. Moreover, the Eu³⁺ emission was very sensitive to pH, so the complex can be used as pH-dependent fluorescence probe or chemosensors.     

SrAl_2B_2O_7:Dy~(3+)材料的制备及其发光性能

采用高温固相法制备了SrAl2B2O7:Dy3+发光材料.在350nm紫外光激发下,测得SrAl2B2O7:Dy3+材料的发射光谱为一个多峰宽谱,主峰分别为480,573和678nm;分别和Dy3+的4F9/2→6H15/2,4F9/2→6H13/2,4F9/2→6H11/2的跃迁发射相对应;监测573nm的发射峰,得到材料的激发光谱为一个多峰宽谱,主峰分别为295,325,350,365,400nm.研究了Dy3+掺杂浓度对SrAl2B2O7:Dy3+材料发射光谱的影响,随着Dy3+掺杂浓度的增大,SrAl2B2O7:Dy3+材料的Iy/Ib逐渐增大,根据Judd-Ofelt理论解释了其原因.随着Dy3+掺杂浓度的增大,Dy3+的4F9/2→6H13/2跃迁产生的573nm发射峰强度先增大,在4%时达到最大值,之后减小,其自身的浓度猝灭机理为电偶极-电偶极相互作用.不同的电荷补偿剂Li+,Na+,K+的引入均使发光强度得到提高,尤其以Li+最佳,发光强度提高了大约33%.     

Combustion synthesis and luminescent properties of a blue-green emitting phosphor: (Ba1.95, Eu0.05)ZnSi2O7:B3+

A blue-green emitting phosphor (Ba_1.95, Eu_0.05)ZnSi₂O₇: B _x ³⁺ was prepared by combustion synthesis and an efficient blue-green emission under near-ultraviolet was observed. The luminescence, crystallinity and particle sizes were investigated by using luminescence spectrometry, X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The emission spectrum shows a single band centered at 503 nm, which corresponds to the 4f ⁶5d ¹ →4f ⁷ transition of Eu²⁺. The excitation spectrum is a broad band extending from 260 to 465 nm, which matches the emission of ultraviolet light-emitting diodes. The optical absorption spectra of the (Ba_1.95, Eu_0.05)ZnSi₂O₇: B _0.06 ³⁺ exhibited band-gap energies of 3.9 eV. The results showed that boric acid was effective in improving the luminescence intensity of (Ba_1.95, Eu_0.05)ZnSi₂O₇, and the optimum molar ratio of boric acid to zinc nitrate was about 0.06. The phosphor (Ba_1.95, Eu_0.05)ZnSi₂O₇: B_0.06³⁺ synthesized by combustion method showed 1.5 times improved emission intensity compared with that of the Ba_1.95ZnSi₂O₇: Eu_0.05²⁺ phosphor under λ _ex = 353 nm.      

Short-living absorption and emission of CsI(Na)

This paper investigates the short-living absorption and the emission of CsI(Na) under a pulsed electron beam (Е_e=0.25 MeV, t_1/2=15 ns and W=0.003…0.16 J/cm²). The bands of singlet self-trapped excitons, as well as Na⁰ and V_k color centers have been detected in the transient absorption spectrum of CsI(Na). It has been found that the activator luminescence spectrum, peaking at 3.0 eV, fits a Gaussian (E_m=3.0 eV and FWHM=0.44±0.02 eV at 80 K) and remains the same at different time delays within 10⁻⁸-10⁻³ s. The decay kinetics of the 3.0 eV emission has one nanosecond exponential component and two microsecond ones with time constants 1.0 and 3.0 μs, which remain unchanged within 78-150 K. It is concluded that the activator emission is due to the radiative annihilation of sodium-perturbed two halide excitons from the non-relaxed singlet state. The pathways of such excitons creation are discussed.     

Growth of α-Al2O3:C crystal with highly sensitive optically stimulated luminescence

In this work, an α-Al₂O₃:C crystal was directly grown by the temperature gradient technique (TGT) using Al₂O₃ and graphite powders as the raw materials. The optical, optically stimulated luminescence (OSL) properties and dosimetric characteristics of as-grown crystal were investigated. As-grown α-Al₂O₃:C crystal shows strong absorption band at 205, 230 and 256 nm. Three-dimensional thermoluminescence (TL) emission spectrum of the crystal shows a single emission peak at ∼415 nm. The OSL decay curve can be fitted to two exponentials, the faster component and the slower component. The OSL response of the crystal shows a linear-sublinear-saturation characteristic. As-grown α-Al₂O₃:C crystal shows excellent linearity in the dose range from 5×10⁻⁶ to 50 Gy. For doses higher than the saturation dose (100 Gy), the OSL sensitivity decreases as the dose increases.