Lebensdauer des 5s5p 3 P 1-Zustands von Strontium

The lifetime of the 5s5p ³ P ₁ state of Sr has been determined with optical double resonance by observation ofrf-transitionsΔm _J =±1 between Zeeman levels of the even isotopes. The measurement yields the value τ(5³ P ₁, Sr)=2.1(3) · 10^?5 sec. A new type of narrowing of optical double resonance signals due to a time-of-flight effect of the radiating atom has been observed and compared with the theory.     

Determination of the 5d6p 3F4-5d2 3F transition probabilities of Ba I

Whether the transitions between 6s5d ³D and 5d6p ³F can be used for laser cooling of barium heavily depends upon the transition probabilities of 5d6p ³F-5d^{2 3}F. Taking the transition 6s5d ³D₃-5d6p ³F⁴ as a scale, the leakage rate of 5d6p ³F₄-5d^{2 3}F was used to evaluate the transition probabilities. 706 nm laser pulses with different durations were applied to a barium atomic beam for 6s5d ³D₃-5d^{2 3}F₄ optical pumping, and the remaining percentages in 6s5d ³D₃ were measured. After exponential fitting, the transition probability of 5d6p ³F₄-5d^{2 3}F_3,4 was determined to be 2.1(4)×10⁴ s^?1, which is in agreement with theoretical calculations using the scaled Thomas-Fermi-Dirac method.     

Luminescence characteristics of the Pr3+ ion in SrAlF5

The paper reports on a study of luminescence and excitation spectra of SrAlF₅:Pr³⁺ (0.5 mol %) polycrystals performed at 10 and 300 K with synchrotron radiation in the range from 5 to 25 eV. The Pr³⁺ ions in SrAlF₅ were shown to emit successively two photons in transitions from the ¹ S ₀ and ³ P ₀ levels. The main energy characteristics of the compound, namely, the position of the 4f → 5d excitation band (5.95–8.0 eV), the energy separation between the ¹ S ₀, 4f and the lowest 5d levels (～0.15 eV), and the SrAlF₅ band gap width (～12 eV), were determined. SrAlF₅:Pr³⁺ was found to possess a number of features not found in other Pr³⁺-activated fluorides.     

Structure of 5-Allyl-2-hydroxy-3-methoxyazobenzene

Abstract

5-allyl-2-hydroxy-3-methoxyazobenzene was preperad by the reaction of 4-allyl-2-methoxyfenol and benzenediazoniumchloride and crystallized from dimethylsulphoxide to yield crystals suitable for analysis. The molecular structure was identified by UV-VIS, IR, ¹H-NMR, ¹³C-NMR and elemental analysis. The crystal structure of the title compound was determined as monoclinic by by single crystal X-Ray diffraction technique. The crystal parameters of this compound are as follows: monoclinic P 2 1/n, a=5.559(2) Å,b=14.900(2) Å, c= 17.573(29 Å, P = 98.58(1)?, V = 1439.3(2) ų, Z = 2, Dx = 0.610 g/cm³, F(OOO) = 284, λ (MoKα) = 0.71070 Å, μ = 0.041 mm^?1. The structure was solved by SHELXS-86 and refined by SHELXL-93. R = 0.09 for 1107 observed reflections with I > 2σ (I).     

The nature of activation centers in Y2SiO5:Pr3+, Gd2SiO5:Pr3+, and Lu2SiO5:Pr3+ crystals

A complex study of the energy spectra and relaxation channels for the excitation energy of activation centers in Y₂SiO₅:Pr³⁺, Lu₂SiO₅:Pr³⁺, and Gd₂SiO₅:Pr³⁺ was performed. An analysis of the low-temperature optical spectra showed that the energy parameters and the character of field splitting of the ¹ D ₂ and ³ H ₄ activator ion terms were substantially different in crystals of different crystallographic types. The pseudosymmetry effect was observed in splitting of the ¹ D ₂ and ³ H ₄ terms of Pr³⁺ ions situated in nonequivalent crystal lattice cation sites of Y₂SiO₅ and Lu₂SiO₅. Activator ions nonuniformly populated nonequivalent cation sites of the Y₂SiO₅ crystal lattice. At high activator ion concentrations (>1 at %), luminescence decay in Y₂SiO₅ could not be described by a simple exponential time dependence. The complex luminescence decay law was caused by activator ion excitation energy migration and capture by acceptors. The role of energy acceptors was played by activator ion dimers.     

Doppelresonanzuntersuchung des Einflusses eines elektrischen Feldes auf die Zeeman-Aufspaltung des 5s 5p 3P1-Terms im SrI-Spektrum

Under the simultaneous action of external electric and magnetic fields the 5s 5p ³ P ₁-level of the even Sr-isotopes splits into three non-equidistant Zeeman-sublevels. In an atomic beam experiment the spacings between the sublevels were investigated by the double resonance method at a magnetic field strength of ca. 22 Oe and at electric field strengths up to ca. 17 kV/cm. From the r.f.-resonance signals the tensor polarizability of the 5s 5p ³ P ₁-level was deduced to be α_ten(³ P ₁)=6.1(8) kHz/(kV/cm)². This value may be used to get an estimate of the oscillator strength of the infrared transitions between the multiplets 5s 5p ³P and 5s 4d ³ D. Taking into account oscillator strengths of electric dipole transitions to other low lying levels one obtainsf(³ P→³ D)≈0.09.     

Optical pumping of the metastable 53P0 level of ODD isotopes of cadmium

Metastable 5³P₀ atoms of ¹¹¹Cd and ¹¹³Cd are optically pumped in an atomic beam. Their magnetic resonances are observed with Landé factors g(³P₀, ¹¹¹ Cd) = (1.090±0.003) × 10^-3 and g(³P₀, ¹¹³Cd) = (1.143 ± 0.003) × 10^-3 which are 1.7 times larger than the g-factors of the 5¹S₀ ground state. This large difference arises from a slight mixing of the 5³P₀ level with the 5³P₁ and 5¹P₁ levels through the hyperfine interaction.     

Stark spectroscopy with the CO2 laser: The ν5 band of 12CD3F

The ν₅ band of ¹²CD₃F was studied using coincidences with the 9.4-μm band of the ¹²C¹⁶O₂ laser and the 9.25-μm band of the ¹²C¹⁸O₂ laser. The resonances were analyzed together with the infrared spectra and recent microwave results to give the following vibration-rotation parameters and dipole moment in the ν₅ state: ν₀ = 1072.35093 (11) cm^?1; B = 0.681137 (4) cm^?1; A₅-A₀ = ?0.01437 (3) cm^?1; Aζ_z = ?0.81453 (3) cm^?1; μ_ν5 = 1.8751 (25) D. The parameters should be useful in assigning some near millimeter laser lines in CD₃F.     

Infrared spectroscopy of the Nd3+ ion in Nd2BaCuO5 and Nd2BaZnO5

Absorption spectra of the Nd³⁺ ion in the Nd₂BaCuO₅ and Nd₂BaZnO₅ ternary oxides were measured within broad spectral (1500–17000 cm^?1) and temperature (4.2–200 K) intervals. The positions and widths of the Stark sublevels were determined. The exchange splittings of the Nd³⁺ Kramers doublets in several multiplets were found for the magnetically ordered state of Nd₂BaCuO₅ (T _N =7.5 K).     

Raman spectroscopic study of the mineral finnemanite Pb5(As3+O3)3Cl

The arsenite mineral finnemanite Pb₅(As³⁺ O₃)₃Cl has been studied by Raman spectroscopy. The most intense Raman band at 871 cm⁻¹ is assigned to the ν₁(AsO₃)³⁻ symmetric stretching vibration. Three Raman bands at 898, 908 and 947 cm⁻¹ are assigned to the ν₃(AsO₃)³⁻ antisymmetric stretching vibration. The observation of multiple antisymmetric stretching vibrations suggest that the (AsO₃)³⁻ units are not equivalent in the molecular structure of finnemanite. Two Raman bands at 383 and 399 cm⁻¹are assigned to the ν₂(AsO₃)³⁻ bending modes. Density functional theory enabled calculation of the position of AsO₃²⁻ symmetric stretching mode at 839 cm⁻¹, the antisymmetric stretching mode at 813 cm⁻¹ and the deformation mode at 449 cm⁻¹. Raman bands are observed at 115, 145, 162, 176, 192, 216 and 234 cm⁻¹ as well. The two most intense bands are observed at 176 and 192 cm⁻¹. These bands are assigned to PbCl stretching vibrations and result from transverse/longitudinal splitting. The bands at 145 and 162 cm⁻¹ may be assigned to Cl Pb Cl bending modes. Copyright © 2009 John Wiley & Sons, Ltd.     

共沉淀法制备Y2SiO5∶Er3+ ,Yb3+ ,Tm3+及其上转换发光性能研究

采用化学共沉淀法制备了系列Y_1.98-2xYb_2x Er_0.02SiO₅(0.00≤x≤0.15)以及Y_1.736Yb_0.24Er_0.02Tm_0.004SiO₅上转换发光材料,比较了室温下Y_1.98-2xYb_2x Er_0.02 SiO₅ (x=0.00,0.08)样品在400—1600 nm范围内的吸收光谱,测量了所有样品在976 nm OPO激光器激发下的上转换发射光谱,以及Er³⁺离子⁴S_3/2(⁴F_9/2)→⁴I_15/2,Tm³⁺离子¹G₄→³H₆荧光衰减曲线和不同激发功率下的上转换蓝光发射强度,从而分析讨论了Er³⁺,Tm³⁺在Y₂SiO₅中的上转换发光机理.研究结果表明:在1250 ℃相对较低的温度下合成了X2型单斜晶系Y₂SiO₅ ∶Ln³⁺(Ln³⁺=Er³⁺,Yb³⁺,Tm³⁺),Yb³⁺的敏化显著增强了样品在976 nm附近的吸收能力,并大幅度加宽了该处的吸收带.分析上转换发射光谱发现:上转换绿光和红光强度都随着Yb³⁺浓度的增加先增强后减弱,但红光的猝灭浓度较高,归因于Er³⁺→Yb³⁺反向能量传递ETU4和Yb³⁺→Er³⁺正向能量传递ETU3过程的发生;上转换蓝光发射是三光子吸收过程,是通过Yb³⁺,Tm³⁺之间三次声子辅助的能量转移方式实现的. 关键词： 上转换 共沉淀 2SiO₅∶Er³⁺')" href="#">Y₂SiO₅∶Er³⁺ 3+')" href="#">Yb³⁺ 3+')" href="#">Tm³⁺     

The perpendicular fundamental v5 of chloroform 12CH35Cl3: high resolution infrared study of the v5 band together with the millimetre-wave rotational spectrum

The infrared spectrum of the perpendicular fundamental v₅ of chloroform around 776 cm^?1 has been studied by applying two high resolution methods. A short range from the central part of the spectrum was measured with a diode laser by using a cold jet sample including chloroform in natural isotopic abundancies. More than 100 rotational lines of ¹²CH³⁵Cl₃ could be assigned. The whole band region was measured by a Fourier transform spectrometer at a resolution of 0.0010cm^?1. In this case an isotopically pure sample of ¹²CH³⁵Cl₃ was used. Starting from the results of the diode laser investigation more than 2000 lines could be assigned with J_max = 91 and K_max = 58. In addition to the infrared spectra, millimetre-wave lines also were measured. A total of 58 lines corresponding to J values 22, 23 and 35 at the excited vibration state v₅ = 1 were assigned and analysed. All the data from three different spectra were simultaneously fitted and, for example, the results v₀ = 775.961 50(3) cm^?1, 98, B₅-B₀ = ?0.180171(22) × 10^?3cm^?1, C₅ ? C₀ = ?0.170 57(15) × 10^?3cm^?1, and (Cζ)₅ = 0.047 5294(11) cm^?1 were obtained.     

Stark-Effekt-Untersuchungen der Hyperfeinstruktur der 5s25d2D3/2- und 5s25d2D3/2-Terme im In I-Spektrum

The level-crossing technique with combined electric and magnetic fields was used to investigate the hyperfine structure of the 5s ²5d ² D _3/2- and 5s ²6d ² D _3/2-stedes of the In I-spectrum. From the shifts of the level-crossing signals due to the Stark effect of the electric field the Stark constantsβ of both states were deduced: 5s ²5d ² D _3/2: ¦β¦=0.33(3) Mc/(kV/cm)² 5s ²6d ² D _3/2: ¦β¦=6(1) Mc/(kV/cm)². By theoretical calculations with wave functions of the Coulomb approximation one can show, that the Stark effect in both states is mainly due to admixtures of the 5s ²6p- resp.5s ²7p-configuration.     

Anharmonic resonances between the v 1 + v ±1 6, v 3 + v ±1 5 + 2v 0 6 and v 3 + v ∓1 5 + 2v ±2 6 vibrational bands of CH3 79Br

The 22 K sub-bands, belonging to the v ₁ + v ^±1 ₆, v ₃ + v ^± ₅ + 2v ⁰ ₆ and v ₃ + v ^±1 ₅ + 2v ^±2 ₆ rovibrational bands of monoisotopic CH₃ ⁷⁹Br, have been identified. An RMS standard deviation of about 0·020 cm^-1 has been achieved by a least squares fit over 619 lines belonging to these 22 sub-bands. For this purpose, a model taking into account (a) anharmonic resonances between (i) v ₁ + v ^±1 ₆, and v ₃ + v ^±1 ₅ + 2v ⁰ ₆, (ii) v ₁ + v ^±1 ₆ and v ₃ + v ^?1 ₅ + 2v ^±2 ₆ and (iii) v ₃ + v ^±1 ₅ + 2v ⁰ ₆ and v ₂ + 2v ₃ + v ^±1 ₅ and (b) Coriolis resonances between the v ₂ and v ₅ modes, was used.     

Pressure effects on 2p5 3p - 2p5 3d transitions in neon

The collisional broadening and shift of four spectral lines of neon (747.2, 748.8, 753.5, 754.4 nm) arising from 2p⁵ 3p - 2p⁵ 3d transitions, emitted from a low-pressure glow discharge in pure neon and neon-helium mixtures have been measured using a Fabry-Perot interferometer. The values of pressure broadening and shift coefficients are determined and analyzed in terms of the impact theory.     

Synthesis and luminescence properties of Er3+-doped Lu3Ga5O12 nanocrystals

The concentration-dependent luminescence properties of sol–gel-derived nanocrystalline Lu_3(1?x)Er_3xGa₅O₁₂ powders (where x=0.01, 0.05 and 0.1) have been studied. Laser-excited luminescence spectra, emission decays and upconversion luminescence of Er³⁺-doped Lu₃Ga₅O₁₂ nanocrystalline samples have been measured. The decay curve of the (²H_11/2,⁴S_3/2) emission exhibits a non-exponential behavior presumably due to cross-relaxation process. Moreover, near-infrared to visible upconversion luminescence has been observed in the green region for 1.0 mol% Er³⁺ ions in Lu₃Ga₅O₁₂ nanocrystals upon 815 nm excitation. The power dependence of the anti-Stokes luminescence suggests that upconversion is probably achieved through the sequential absorption of two photons. To the best of our knowledge, this is the first report on the preparation and optical properties of Er³⁺-doped Lu₃Ga₅O₁₂ in the form of nanocrystalline powders.     

A comparative study of the optical properties of Fe3+ in ordered LiGa5O8 and LiAl5O8

Measurements are reported on the fluorescence and excitation spectra of Fe³⁺-doped LiGa₅O₈ in the ordered phase. Spectral determinations were made with powder samples containing 0.01 to 1% atomic weight of Fe³⁺, within the temperature range 300 K to 25 K. A comparison is presented between the optical properties of trivalent iron in lithium gallate and in lithium aluminate, LiAl₅O₈, both in their ordered phases. The best fit with crystal field parameters B, C, and Dq, yields the following values for these parameters: Dq = 906 cm^-1, B = 594 cm^-1, and C = 3 737 cm^-1. As is the case with LiAl₅O₈:Fe³⁺, the Stokes shift in LiGa₅O₈:Fe³⁺ is very large, 3 624 cm^-1, although somewhat smaller than the 4 300 cm^-1 seen in LiAl₅O₈:Fe³⁺.     

Phase Transition in the Compound NH3(CH2)5NH3TlCl5

Penthylene diammonium pentachlorothallate(III) exhibits a phase transition at 316 K <artwork name="GPHT21157eu1"> This transition has been characterized by optical birefringence, dielectric measurements differential scanning calorimetry and spectroscopic measurements on polycrystalline samples. The space group and the cell parameters of phase I were determined by X-ray diffraction from single crystals. Phase I has space group P2₁2₁2₁, with Z = 4, a = 7.696(3), b = 13.2890(17) and c = 13.503(18) Å. The transition is both displacive and order-disorder involving mainly conformational changes of the organic chain [NH₃(CH₂)₅NH₃]²⁺ coupled with distortion of the TlCl₆ octahedra. This behaviour and the crystal dynamics will be discussed and compared with those found in the literature for homologous compounds.     

Absorption and luminescence of Nd3+:Y3Al5O12

In this paper there are briefly summarized the results of our experimental measurements of the fluorescence spectra, originating in levels of the⁴ F _3/2 term and terminating on the first two terms of the⁴I multipet, and the results of the absorption spectra at room temperature (RT) and at liquid-nitrogen temperature (NT) from which Nd³⁺: Y₃Al₅O₁₂ energy-level diagram was determined. Further, using the splitting of the⁴F_3/2,⁴F_5/2 and⁴F_7/2 terms the crystal-field parameters were calculated.     

Synthesis and up-conversion luminescence properties of Ho3+, Yb3+ co-doped BaLa2ZnO5

Up-conversion phosphors BaLa₂ZnO₅ co-doped with Ho³⁺/Yb³⁺ were synthesized by high temperature solid-state reaction method. The phase composition of the phosphors was characterized by X-ray diffraction (XRD). The structure of BaLa₂ZnO₅: 0.75% Ho/15% Yb phosphor was refined by the Rietveld method and results showed the decreased unit cell parameters and cell volume after doping Ho³⁺ and Yb³⁺, indicating Ho³⁺ and Yb³⁺ have successfully replaced La³⁺. Under the excitation of 980 nm diode laser, the strong green and weak red up-conversion emissions centered at 548 nm, 664 nm and 758 nm were observed, which originating from ⁵S₂, ⁵F₂→⁵I₈, ⁵F₄→⁵I₈ and ⁵S₂, ⁵F₂→⁵I₇ transitions of Ho³⁺ ions, respectively. The optimum doping concentrations of Ho³⁺ and Yb³⁺ were determined to be 0.75% and 15%, and the corresponding Commission International de L'Eclairage (CIE) coordinates are calculated to be x=0.298 and y=0.692. The related UC mechanism of Ho³⁺/Yb³⁺ co-doped BaLa₂ZnO₅ depending on pump power was studied in detail. The results indicate that BaLa₂ZnO₅: Ho³⁺/Yb³⁺ can be an effective candidate for up-conversion yellowish-green light emitter.