β-Na(Y1.5Na0.5)F6:Tm—A blue upconversion phosphor

A luminescent material β-Na(Y_1.5Na_0.5)F₆ doped with Tm³⁺ was synthesized by a solid-state reaction method for a steady phosphor of blue upconversion. Under the 671 nm laser excitation, the green emission band of 511 nm due to the ¹D₂→³H₅ transition is obtained for the first time, while the ultraviolet emission band is also observed at 368 nm, associated with the ¹D₂→³H₆ transition. Especially, a wide band of blue emissions is obtained at the wavelength region of 440-490 nm, originated mainly from the ¹D₂→³F₄ (450 nm) and ¹G₄→³H₆ (471-487 nm) transitions, which have potential application in tunable solid-state blue laser of Tm³⁺. The upconversion mechanism is explored in terms of the energy-level structures of Tm³⁺ ion and the power dependence of upconverted emission intensity, which is believed to be performed by excited-state absorption.     

Double Fluorescence Conversion in Ultraviolet and Visible Region for Some Praseodymium Complexes of Aromatic Carboxyates

Four praseodymium complexes of aromatic carboxylates (benzoate, 4-tert-butylbenzoate, 2-benzoylbe-noate, and benzimidazole-5-carboxylate) have been synthesized and characterized, whose photophysical properties have been studied with ultraviolet spectra, phosphorescence spectra, and fluorescence spectra. The fluorescent emission spectra of all praseodymium complexes show two emission peaks under the excitation band of 245 nm at about 395 and 595 nm respectively, while one peak under 415 nm at about 595 nm, which attributed to be ¹S₀ → ¹I₆ (395 nm) transition and the characteristic emission ¹D₂ → ³H₄ (595 nm) transition of Pr³⁺ ion. The ¹S₀ → ¹I₆ transition can be ascribed as the transition of charge transfer state, and the ¹D₂ → ³H₄ can be further proved that there exists an antenna effect in the fluorescence of praseodymium with aromatic carboxylic acids. In conclusion, the praseodymium complexes systems can realize the double fluorescent conversion in both ultraviolet and visible region and can be further studied the application of this conversion.     

Resonances at collisions of slow electrons with cadmium atoms and ions

Using the crossed-beam method and a hypocycloidal electron spectrometer, the energy dependence of the ionization cross section for the cadmium atom has been studied in the near-threshold region and the elastic scattering of slow electrons at an angle close to 180° by Cd⁺ ions was studied for the first time. Within the region under study (0–7 eV above the first atomic ionization potential), a resonance structure determined by the contribution of atomic autoionization states is revealed in both the ionization curve and differential cross section of elastic scattering. The structure in the measured curves has been analyzed with the use of data on the ejected-electron spectra obtained under the excitation of autoionization states of Cd atoms, as well as the data on the optical excitation functions for the atomic spectral lines at λ=430.7 nm (5¹ P ₁-8¹ S ₀), 515.5 nm (5¹ P ₁-7¹ S ₀), 298.0 nm (5³ P ₂-6³ D _j ), and 361.0 nm (5³ P ₂-5³ D _j ).     

CW ultraviolet saturation spectroscopy of the 6p 3P0-9s 3S1 transition in mercury at 246.5 nm

We have measured the even isotope structure of the 6p ³P₀-9s ³S₁ transition in mercury at 246.5 nm using saturated absorption spectroscopy with radiation produced as the sum frequency of a 363.8 nm argon ion laser and an LD700 ring dye laser in ADP. This is the first use of cw sum-frequency mixing in nonlinear laser spectroscopy in the ultraviolet. No previous cw Doppler-free measurements have been reported at wavelenghts below 294.5 nm     

Structure hyperfine du niveau 6s6d3D1 de l'isotope 199 du mercure par interferometrie fabry-perot

The h.f.s of the 6s6d³D₁ state of ¹⁹⁹Hg has been measured by Fabry-Perot interferometry, using the 6³P₀-6³D₁ transition and taking into account the “forbidden” transition 6³P₀-6¹D₂. Two independent results are obtained: 383,67 ± 0,61 mK and 383,38 ± 0,25 mK, which agree with the theoretical value.     

Saturated absorption spectroscopy in the ultra-violet with a continuous-wave,frequency-doubled,ring dye laser; even isotope shifts on the 6d3D1-6p3P0 transition of HgI

A novel, single-frequency, continuous-wave, ring, dye laser with intra-cavity frequency-doubling has been developed, and used to carry out saturated absorption spectroscopy on the 6s6d³D₁-6s6p³P₀ transition of Hg I at 296.7 nm. Even isotope shifts have been measured by this technique on this transition and are: Hg204-202, 350 ± 10 MHz; Hg202-200, 345 ± 10 MHz; Hg200-198, 310 ± 10 MHz. The shift on transitions from the hyperfine state 6s6d³D₁ ($\text{F =}\text{3}\text{2}$) between Hg199 and Hg201 has also been measured, and is 225 ± 10 MHz.     

Influence of the 61 S 0–63 P 1 resonance on continuous Lyman-α generation in mercury

Continuous coherent radiation in the vacuum ultraviolet at 122 nm (Lyman-α) can be generated using sum-frequency mixing of three fundamental laser beams in mercury vapor. One of the fundamental beams is at 254 nm wavelength, which is close to the 6¹ S ₀–6³ P ₁ resonance in mercury. Experiments have been performed to investigate the effect of this one-photon resonance on phase-matching, absorption and the nonlinear yield. The efficiency of continuous Lyman-α generation has been improved by a factor of 4.5.     

Luminescence of Ca(NbO3)2:Pr at ambient and high hydrostatic pressure

In this contribution, photoluminescence and time-resolved photoluminescence spectra of Ca(NbO₃)₂ doped with Pr³⁺ obtained at high hydrostatic pressure up to 72 kbar applied in a diamond anvil cell are presented. At ambient conditions, the emission spectrum obtained in the time interval 0-1 μs is dominated by spin-allowed transitions from the ³P₀ state. On the other hand, transitions from ¹D₂, characterized by a decay time equal to 30 μs dominate the steady-state luminescence.At pressures lower than 60 kbar, the continuous wave emission spectrum consists of sharp lines peaking between 600 and 625 nm, related to the ¹D₂→³H₄ transition and three lines at 500, 550 and 650 nm related to emission transitions originating from the ³P₀ level of Pr³⁺. The emission from the ¹D₂ excited state depends weakly on the pressure. Its decay time decreases from 33 μs at ambient pressure to less than 22 μs at 68 kbar. On the other hand, the ³P₀ emission is strongly pressure dependent. At pressures of 60 kbar and higher, the Pr³⁺ emission intensity from the ³P₀ state decreases. This is accompanied by a strong shortening of the luminescence decay time.The observed pressure quenching of the f-f emission transitions and the concomitant lifetime shortening have been attributed to increasing crossover from the ³P₀ state of Pr³⁺ to a Pr³⁺-trapped exciton state.     

The luminescent properties of CaYBO4:Ln(Ln=Eu, Tb) under UV-VUV range

The luminescent properties of CaYBO₄:Ln(Ln=Eu³⁺, Tb³⁺) were investigated under ultraviolet (UV) and vacuum ultraviolet (VUV) region. The CT band of Eu³⁺ at about 245 nm blue-shifted to 230 nm in VUV excitation spectrum; the band with the maximum at 183 nm was considered as the host lattice absorption. For the sample of CaYBO₄:0.08Tb³⁺, the bands at about 235 and 263 nm were assigned to the f-d transitions of Tb³⁺ and the CT band of Tb³⁺ was calculated according to Jφrgensen's theory. Under UV and VUV excitation, the main emission of Eu³⁺ corresponding to the ⁵D₀-⁷F₂ transition located at about 610 nm and two intense emission of Tb³⁺ from the ⁵D₄-⁷F₅ transition had been observed at about 542 and 552 nm, respectively. With the incorporation of Gd³⁺ into the host lattice of CaYBO₄, the luminescence of Tb³⁺ was enhanced while that of Eu³⁺ was decreased because of their different excitation mechanism.     

Inner-shell excited quartet states in Li-like O<Superscript>5+</Superscript> and Ne<Superscript>7+</Superscript> ions

First laser spectroscopic measurements of the 6s5d³D₁-6s6p¹P₁ and 6s5d³D₂-6s6p¹P₁ transitions in several isotopes of atomic barium have been performed. The hyperfine structure of these transitions was optically resolved and isotope shifts for even and odd isotopes were determined. The isotope shifts show a deviation from their expected behavior for odd isotopes in an analysis based on King-plots. This observation puts atomic structure calculations at test because available theories do not predict this. A profound understanding of the wavefunctions for heavy alkaline earth systems like barium (Ba) and radium (Ra) is essential for a theoretical evaluation of their sensitivity to fundamental symmetry breaking effects such as they could be observed, e.g., through permanent electric dipole moments. Further the absolute frequency of the 6s^{2 1}S₀-6s6p³P₁ intercombination line in ¹³⁸Ba was determined to be 12 636.6232(1) cm^-1.     

Effect of annealing and Mn doping on the photoluminescence of strontium tartrate crystals

Strontium tartrate crystals (STC) were grown in gel using the single tube diffusion method. Powder XRD and FTIR spectroscopy were used for the characterization of the crystal. The optical band-gap (Eg) of STC is found to be 5.46 eV. Photoluminescence (PL) spectra of STC are recorded at different annealing temperature and concentration of dopant Mn. The spectral peaks (λ_em) of strontium tartrate photoluminor lie around 417, 440, 513 and 620 nm with excitation wavelength (λ_exc)=379 nm. The peaks at 417, 513 and 620 nm correspond to transitions ²P_1/2⁰→²S_1/2, ¹D⁰→³P⁰ and ¹S→³P⁰, respectively of Sr. The PL peak observed around 440 nm corresponds to the a⁴D_7/2→a⁶S_5/2 transition of Mn.     

Measurement of the isotope shift of the 63 P 1 ↔53 D 1 transition of ytterbium by using a diode oscillator fiber amplified laser

We demonstrated a Diode Oscillator Fiber Amplification (DOFA) system in order to study the 6³ P ₁ ?5³ D ₁ (1539 nm) transition line of a neutral ytterbium atom that is accessed by the stepwise excitation of the ground state. The frequency of the DOFA system was doubled by a MgO:PPLN crystal for the resonant excitation of the 6¹ S ₀ ?6³ P ₁ transition. The frequency of the second harmonic beam was stabilized to the 6¹ S ₀ ?6³ P ₁ transition of each isotope with the stability of about 2 MHz. We performed absorption spectroscopy on the 6³ P ₁ ?5³ D ₁ (1539 nm) transition after the velocity selective excitation by the frequency-doubled beam. The isotope shifts in the 6³ P ₁ ?5³ D ₁ (1539 nm) transition were directly measured for the first time. The relative isotope shifts from ¹⁷⁴Yb were measured as ?105.8 MHz and 109.7 MHz for ¹⁷⁶Yb and ¹⁷²Yb, respectively.     

Ultraviolet spectroscopy of Pr+3 and its use in making ultraviolet filters

Sputtered deposited thin films of AlN:Pr and GaN:Pr emit in ultraviolet–visible and visible regions of the spectrum, respectively, under electron excitation in cathodoluminescence apparatus. The goal is to study the ultraviolet emission from Pr⁺³ when doped in nitride semiconductor hosts. Luminescence peaks at a wavelength of 295 nm (4.2 eV), 335 nm (3.7 eV) and 385 nm (3.24 eV) are observed as a result from ¹S₀ → ¹G₄, ¹S₀ → ¹D₂ and ¹S₀ → ¹I₆ transitions, respectively. However the ¹S₀ → ¹G₄ and ¹S₀ → ¹D₂ transitions are not observed when Pr⁺³ is doped in GaN host. The bandgap of GaN absorbs the ultraviolet radiation emitted from Pr⁺³ and hence GaN can be used as ultraviolet filter for radiation shielding and protection purposes. AlN is transparent to ultraviolet due to its wide bandgap of 6.2 eV.     

Y2O3:Yb3+,Tm3+纳米材料的可见及紫外上转换发光

通过燃烧法制备了Yb³⁺-Tm³⁺共掺的Y₂O₃纳米粉体,并对样品在980 nm激光照射下的上转换发光特性进行了研究.实验发现,样品在可见光区域能够产生强烈的蓝色发光(476 nm和487 nm)和较弱的红色发光(约650 nm),而且同时观察到了两个紫外发光峰¹I₆→³H₆ (~297 nm)和^{1关键词： 2O₃:Yb3+')" href="#">Y₂O₃:Yb3+ 3+}')" href="#">Tm³⁺ 上转换光谱 敏化 紫外发光     

Multi-wavelength excimer ultraviolet sources from a mixture of krypton and iodine in a dielectric barrier discharge

New ultraviolet (UV) sources (excimer lamps) have been demonstrated using mixtures of krypton and iodine in a high-pressure dielectric barrier discharge to provide intense multi-wavelength radiation at λ=183 nm (atomic iodine line, ⁴ P _5/2?² P _3/2), 191 nm (KrI^*, B _1/2?X _1/2), 206 nm (atomic iodine line, ² P _3/2?² P _1/2), and 342 nm (I^* ₂, D _1/2?X _1/2). The characteristics of the optical emission spectra of the atomic species and the excited dimers (excimers) formed for different total gas pressures and in the presence of a buffer gas have been investigated. The highest intensity, at 183 nm, is obtained at pressures up to 1 bar while the overall emission spectra can be controlled by adjusting the total pressure. The results show that these strong multi-wavelength lamps offer an interesting alternative to conventional UV sources. Received: 1 March 2000 / Revised version: 5 April 2000 / Published online: 30 June 2000     

Multiphoton ultraviolet and visible upconversion luminescence of TmYb co-doped oxyfluoride glass

The ultraviolet upconversion luminescence of Tm³⁺ ions sensitized by Yb³⁺ ions in oxyfluoride glass when excited by a 975 nm diode laser was studied in this paper. One typical ultraviolet upconversion luminescence lines positioned at 362.3 nm was found. It can be attributed to the five-photon upconversion luminescence transition of ¹D₂ → ³H₆. Several visible upconversion luminescence lines at 451.1 nm, (477.9 nm, 462.5 nm), 648.7 nm, (680.5 nm, 699.5 nm) and (777.5 nm, 800.7 nm) were found also, which results from the fluorescence transitions of five-photon ¹D₂ → ³F₄, three-photon ¹G₄ → ³H₆, three-photon ¹G₄ → ³F₄, two-photon ³F₃ → ³H₆ and two-photon ³H₄ → ³H₆ of Tm³⁺ ion, respectively. The theoretical analysis suggests that the upconversion mechanism of the 362.3 nm ¹D₂ → ³H₆ upconversion luminescence is the cross energy transfer of {³H₄(Tm³⁺) → ³F₄(Tm³⁺), ¹G₄(Tm³⁺) → ¹D₂(Tm³⁺)} and {¹G₄(Tm³⁺) → ³F₄(Tm³⁺), ³H₄(Tm³⁺) → ¹D₂(Tm³⁺)} between Tm³⁺ ions. In addition, the upconversion luminescence of ¹G₄ and ³H₄ state results from the sequential energy transfer {²F_5/2(Yb³⁺) → ²F_7/2(Yb³⁺), ³H₄(Tm³⁺) → ¹G₄(Tm³⁺)} and {²F_5/2(Yb³⁺) → ²F_7/2(Yb³⁺), ³F₄(Tm³⁺) → ³F₂(Tm³⁺)} from Yb³⁺ ions to Tm³⁺ions, respectively.     

Hg蒸汽中通过双光子共振四波差频产生调谐真空紫外辐射

利用Hg原子6¹S₀—6¹D₂和6¹S₀—6³D₂双光子共振的四波差频(2ω₁—ω₃),获得了真空紫外相干辐射(ω₄)。当入射光之一(ω₃)波长调谐时,产生的真空紫外光也是调谐的,调谐范围为184.9-187.5nm.本文对非线性频率变换过程的机 关键词：     

Effect of concentration on the luminescence of Eu ions in nanocrystalline La2O3

Nanocrystalline powders with various Eu³⁺ concentration (from 1 to 10 mol %) doped La₂O₃ were prepared via a combustion route. Their structure and morphology were characterized using X-ray diffraction (XRD) and High-resolution transmission electron microscopy. The emission spectra of the as-synthesized samples show that the strongest emission position is centered at 626 nm corresponding to ⁵D₀→⁷F₂ transition of Eu³⁺ ions and the intensity change of 626 nm emission is considered as a function of ultraviolet (240 nm) irradiation time. The excitation spectra at 626 nm monitoring indicate that the charge transfer state band is varies with different Eu³⁺ ion concentration. These results are attributed to the surface defects of the nanocrystals.     

Ground-state measurement of Pr<Superscript>3+</Superscript> in Y<Subscript>2</Subscript>O<Subscript>3</Subscript> by photoconductivity

1 at % Pr³⁺-doped Y₂O₃ single-crystal fibers were prepared using a laser-heated pedestal growth method. The emission and excitation spectra of the fibers were measured. The emissions of 4f-4f transitions from ¹ D ₂ to the ³ H ₄ and ³ H ₅ states are found at 620 and 720 nm, respectively. The ³ P ₂, ³ P ₁, ¹ I ₆, and ³ P ₀ 4f-4f absorptions are observed at 456, 472, 482, and 492 nm, respectively. A 4f-5d absorption band is detected at 288 nm. Photoconductivity measurements show that the 4f-5f transition of Pr³⁺ around 285 nm produces a direct photocurrent. Taking the onset of photocurrent to be at 320 nm, the ground state of Pr³⁺ is determined at 1.7 eV above the valence band of the host. The text was submitted by the authors in English.     

Luminescence properties of red-emitting praseodymium-activated BaTi4O9 phosphor

The photoluminescence and low-voltage cathodoluminescence characteristics of BaTi₄O₉:Pr³⁺ were investigated. The excitation band of intervalence charge transfer (IVCT) of BaTi₄O₉:Pr³⁺ emerged distinctly at 330 nm. The resultant emissions appeared at 606-643 nm corresponding to the ¹D₂→³H₄ transition. In BaTi₄O₉:Pr³⁺, the emission of ³P₀→³H₄ transition at 490 nm was not observed. The results were in a pure red color emission.