Experimental stark parameters for some lines of neutral carbon,oxygen, and sulfur

Profile measurements for some multiples of neutral oxygen, carbon and sulfur have been carried out in a wall-stabilized arc. A 3.4 m Ebert spectrograph (with a dispersion of 1.1 mm/Å) adapted to simultaneous photoeletric scanning of 2 sources was used. Different gas mixtures (Ar + CO₂, Ar + SF₆, Ar + O₂) containing a small quantity of hydrogen were used for production of plasmas. Arc currents between 12 and 102 A yielded electron densities from 0.76 to 7.1 x 10¹⁶cm^-3 and temperatures between 9000 and 12,000 K. Half-widths and shifts of 7 multiplets were determined and compared with theoretical and experimental data. Good agreement was generally found except for C(I) (4771 Å), where the difference between our results and those of Nubbemeyer and Wende is too large. Stark parameters of components for the well-resolved multiplet C(I) (6) and other multiplets in the same transition arrays show the behavior expected for plasma-broadened line parameters.     

THE INFLUENCE OF THE ADMIXING OF DIFFERENT MULTIPLETS ON THE SPIN MAGNETIC MOMENT AND FARADAY EFFECT OF HARE EARTH IONS IN GARNETS

The influence of the admixing of the excited multiplets of the ground configuration with the ground multiplet on the spin magnetic moment of the crystal- field-and exchange-interaction-split ground state, the Faraday rotation and the magneto-optic coefficient induced by the rare earth ions in rare-earth-substituted garnets Y_3-xR_xFe₅O₁₂ (R=Ce and Pr) has been calculated in this paper. It is found that, in the case of Ce³⁺ ions, the admixing of the 4f^{1 2}F_7/2 multiplet with the ²F_5/2 multiplet makes the spin magnetic moment of the crystal-field- and exchange-interaction-split ground state increase by 140% and the Faraday rotation increase by 180% at 633nm wavelength, and 150% at 1150nm at 294 K. In the case of Pr³⁺ ions, the admixing of the 4f^{2 3}H₅ multiplet with the ³H₄ multiplet makes the spin magnetic moment of the crystal-field- and exchange-interaction-split ground state increase by 34% and the Faraday rotation increase by 59% at 294K. The admixing of different multiplets of the Ce³⁺ ions makes the ratio between the magneto-optic coefficients at 50 and 294K increase by 7% at 633nm wavelength and 15% at 1150nm.     

Wavelength coincidence of allowed and intercombination multiplets in N III and O IV: A density and/or temperature diagnostic

Two multiplets of N III with different intensity dependence on source conditions fall in the same wavelength interval near 1750 Å, and the analogous multiplets in O IV also lie close together. It is suggested that the multiplet pair can be useful for diagnostic purposes. The calculated ratios are consistent with available observations. A preliminary inspection of solar flare spectra shows the presence of the higher-density-indicating allowed multiplet in O IV.     

Stark broadening of some C(I) and N(I) vacuum ultraviolet lines

Stark widths of 11 C(I) lines and 3 N(I) multiplets were measured in the wavelength range 1310 Å ⩽ λ ⩽ 2583 Å. Gas mixtures (Ar+CO₂, Ar+N₂ and Ar+CO₂+N₂) were used for production of plasmas in a wall-stabilized arc under atmospheric pressure. Results were provided by five experiments (T varies from 13,370 to 13,950 K and N_e from 1.13 x 10¹⁷ cm^-3 to 1.35 x 10¹⁷ cm^-3. Stark shifts were measured for 2 C(I) lines and the ion-broadening parameter A was evaluated for 7 C(I) lines using different methods. The Stark widths and shifts are generally in reasonable agreement with other experimental or theoretical values, while the estimated A values are much higher than those predicted by Griem's theory.     

He2+离子和H2,O2分子碰撞过程中电子俘获和靶激发的发射截面

实验结果表明:在He²⁺和H₂,O₂碰撞过程中存在着双电子俘获而产生激发态的过程,同时也存在着单电子俘获而产生激发态的过程。在靶H₂,O₂直接激发过程中,测量到了巴耳末系H_α,H_β,H_γ和OI的发射谱。本文给出随入射离子速度变化的Hel,Hell和H_α,H_β,H_γ,O 关键词：     

Theoretical studies of the local structures and electron paramagnetic resonance parameters for Cu2+ center in Zn(C3H3O4)2(H2O)2 single crystal

The electron paramagnetic resonance (EPR) parameters (g factors g_xx, g_yy, g_zz and hyperfine structure constants A_xx, A_yy, A_zz) are interpreted by taking account of the admixture of d-orbitals in the ground state wave function of the Cu²⁺ ion in a Zn(C₃H₃O₄)₂(H₂O)₂ (DABMZ) single crystal. Based on the calculation, local structural parameters of the impurity Cu²⁺ center were obtained (i.e. R_a≈1.92 Å, R_b≈1.96 Å, R_c≈1.99 Å). The theoretical EPR parameters based on the above Cu²⁺?O^2? bond lengths in the DABMZ crystal show good agreement with the observed values and some improvements have been made as compared with those in the previous studies.     

Infrared transmission study of Pr<Subscript><Emphasis Type="Bold">2</Emphasis></Subscript>CuO<Subscript><Emphasis Type="Bold">4</Emphasis></Subscript> crystal-field excitations

We present an infrared crystal-field study of Pr₂CuO₄ single crystals and thin films. Excitations from the ground state multiplet ³H₄ to the ³H₅, ³H₆, ³F₂ and ³F₃ excited multiplets are observed in both single crystals and thin films. A precise set of crystal-field parameters, that reproduces the energy and the symmetry of the levels, is determined. Received 25 April 2001     

X-ray study of some spinels containing gallium and manganese

The ternary oxides CrMnGaO₄, NiMnGaO₄, CuMnGaO₄ and ZnMnGaO₄, crystallize in the cubic spinel structure with lattice parametera=8.41±0.02 Å, 8.34±0.02 Å, 8.36±0.02 Å and 8.32±0.02 Å, respectively. The oxidation state of manganese in these spinels was determined x-ray spectroscopically. The site distribution was determined from the structural properties and calculated site preference energies of cations in the lattice. The ionic structures were found to be Ga³⁺ [Mn²⁺ Cr³⁺] O ₄ ^2? . Ga³⁺ [Cu²⁺ Mn³⁺] O ₄ ^2? , Mn²⁺ [Ga³⁺ Ni³⁺] O ₄ ^2? and Zn²⁺ [Mn³⁺ Ga³⁺] O ₄ ^2? .     

Absolute photoabsorption cross sections for H2O and D2O from λ 180–790 Å

Absolute photoabsorption cross sections for H₂O and D₂O have been measured photoelectrically from λλ 180 to 790 Å using synchrotron radiation. The cross sections increase smoothly with wavelength to ～λ610 Å, with both H₂O and D₂O displaying a broad absorption band extending above a nearly linear background from λλ 400 to 490 Å. The continuum has a maximum of ～ 22.5 Mb at λ 640 Å. Above λ 615 Å, superimposed on the continuum, a diffuse structure appears which is similar to the vibrational structure of the ²B₂ states of H₂O⁺ and D₂O⁺ as observed in photoelectron spectra. The structure is believed to arise from excitation of a 1b₂ electron to the vibrational levels of a Rydberg orbital with n¹ ≈ 2.64.     

Quenching of excited strontium atomic state measured in H2- and CO-flames

The efficiency of resonance fluorescence, Y, of the strontium resonance line (¹P₁→¹S₀ transition) at 4607.33 Å was measured in CO/N₂O, CO/O₂/Ar, and H₂/O₂/CO₂/N₂ flames at atmospheric pressure. From these data, the specific quenching cross sections, σ_qu, for CO₂ and CO were found to be (60 ± 10) Ų and  (300 ± 60) Ų, respectively. The experimental cross sections were confronted with the intermediate ionic-state curve-crossing model and chemical quenching model, respectively.     

Electronic-excitation transfer collisions in flames—II temperature dependence of the quenching of Na(32P)-doublet by H2 and O2

Effective cross sections for quenching of the Na(3²P)-doublet by H₂ and O₂ molecules have been measured in flames in the temperature range 1500–2500 K. The H₂-cross section decreases from (9.3±1.0) Ų at 1500 K to (6.8±1.0) Ų at 2500 K. The O₂-cross section decreases from (39±2) Ų at 1720 K to (31±2) Ų at 2500 K. A critical comparison of the flame values with previous literature data on the H₂-cross section at lower temperatures shows that it decreases systematically when the temperature rises from about 400 to 2500 K.     

Polymorphism in Bi2Sn2O7

Single crystals of Bi₂Sn₂O₇ were grown in a Bi₂O₃ flux. Phase transitions were identified at about 90 and 680° using X-ray, SHG, DSC, dielectric, and optical data. γ-Bi₂Sn₂O₇, which exists above 680°C is centric and cubic with a = 10.73 Å at 700°, and it probably has the ideal pyrochlore structure. β-Bi₂Sn₂O₇, which exists between 680° and about 90°C, is acentric but remains cubic with a = 21.40 Å. α-Bi₂Sn₂O₇, which exists from about 90°C to below room temperature, is acentric and noncubic, probably tetragonal with a = 21.328 and c = 21.545 Å. The α-β transition is first order, and the β-γ transition appears to be second order. Substitutions of Pb²⁺ or Cd²⁺ for Bi³⁺ and of Ga³⁺, Rh³⁺ Sc³⁺, In³⁺, Sb⁵⁺ Nb⁵⁺ or Ta⁵⁺ for Sn⁴⁺ lower the α-β transition temperature.     

Effect on the EPR and local lattice structure distortion of V3+ ion doping corundum crystal: three models studied

This paper reports on the application of conventional models (the displacement model and the elongation model) and the four-parameter model in detecting the local molecular structure of a coordination complex. By diagonalizing the complete energy matrices, the EPR parameters and optical spectra as well as the local distortion structure for V³⁺ ion in the Al₂O₃ : V³⁺ system have been studied using the three models. The four-parameter model is shown to provide a significant improvement over the conventional models. Based on these calculations, it was found that when V³⁺ is doped in Al₂O₃, the distance between upper and lower ligand oxygen plane increases by 0.16097 Å and the shifts of O^2? ions in the upper and lower ligand oxygen planes expand by 0.07076 Å and 0.004066 Å, respectively. To understand the detailed physical and chemical properties of the doped Al₂O₃, the contributions of the spin-orbit coupling to the zero-field splitting for V³⁺ ion are investigated.     

Syntheses and structure characterization of inorganic/organic coordination polymers: Ag(dpa), Co(O3PH)(4,4′-bpy)(H2O), Zn(O3PH)(4,4′-bpy)0.5 and Mn[O2PH(C6H5)]2(4,4′-bpy) (dpa=2,2′-dipyridylamine; 4,4′-bpy=4,4′-bipyridine)

Four novel coordination polymers: Ag(dpa) I, Co(O₃PH)(4,4′-bpy)(H₂O) II, Zn(O₃PH)(4,4′-bpy)_0.5 III and Mn[O₂PH(C₆H₅)]₂(4,4′-bpy) IV (dpa=2,2′-dipyridylamine; 4,4′-bpy=4,4′-bipyridine), were synthesized by microwave heating and characterized by X-ray crystallography. I crystallizes in monoclinic space group P21/n with a=11.576(2) Å, b=5.585(2) Å, c=15.243(4) Å, β=109.00(2)°, V=931.8(3) ų. II crystallizes in monoclinic Cc space group with a=22.477(7) Å, b=5.280(1) Å, c=10.404(4) Å, β=96.08(3)°, V=1227.8(7) ų. III crystallizes in monoclinic P21/c space group with a=9.758(2) Å, b=7.449(3) Å, c=10.277(2) Å, β=100.02(2)°, V=735.6(4) ų. IV crystallizes in monoclinic space group P2/c with a=10.174(1) Å, b=11.817(3) Å, c=18.784(4) Å, β=102.14(1)°, V=2207.8(8) ų. I consists of linear metal–metal chains wrapped by dpa ligands. II and III consist of two-dimensional M^II(O₃PH) inorganic sheets cross-linked by 4,4′-bpy ligands, while IV is formed by Mn[O₂PH(C₆H₅)]₂ sheets cross-linked by 4,4′-bpy ligands. I exhibits two-step thermal decomposition at ~200 and ~250°C, resulting in the reduction of Ag⁺ to Ag metal. II loses its coordination water at ~100°C, leaving vacant coordination sites at Co²⁺ ions, while the original framework remains intact. The removal of 4,4′-bpy in II–IV occurs at elevated temperatures above 250, 200 and 400°C respectively.     

Crystalline structure and optical spectroscopy of Er3+-doped KGd(WO4)2 single crystals

4 )₂ single crystals doped with Er³⁺ have been grown by the flux top-seeded-solution growth method. The crystallographic structure of the lattice has been refined, being the lattice constants a=10.652(4), b=10.374(6), c=7.582(2) Å, β=130.80(2)°. The refractive index dispersion of the host has been measured in the 350–1500 nm range. The optical absorption and photoluminescence properties of Er³⁺ have been characterised in the 5–300 K temperature range. At 5 K, the absorption and emission bands show the (2J+1)/2 multiplet splittings expected for the C₂ symmetry site of Er in the Gd site. The energy positions and halfwidths of the 72 sublevels observed have been tabulated as well as the cross sections of the different multiplets. Six emission band sets have been observed under excitation of the ⁴F_7/2 multiplet. The Judd–Ofelt (JO) parameters of Er³⁺ in KGW have been calculated: Ω₂=8.90×10^-20 cm², Ω₄=0.96×10^-20 cm², Ω₆=0.82×10^-20 cm². Lifetimes of the ⁴S_3/2, ⁴F_9/2, and ⁴I_11/2 multiplets have been measured in the 5–300 K range of temperature and compared with those calculated from the JO theory. A reduction of the ⁴S_3/2 and ⁴I_11/2 measured lifetimes with increasing erbium concentration has been observed, moreover the presence of multiphonon non-radiative processes is inferred from the temperature dependence of the lifetimes. Received: 15 December 1997/Revised version: 10 July 1998     

Heavy Quark Hadron Mass Scale

Without the spin interactions the hadron masses within a multiplet are degenerate. The light quark hadron degenerate multiplet mass spectrum is extended from the 3 quark ground state multiplets at J^P = 0⁻, ½⁺, 1⁻ to include the excited states which follow the spinorial decomposition of SU(2) × SU(2). The mass scales for the 4, 5, 6,… quark hadrons are obtained from the degenerate multiplet mass m₀/M = n²/α with n = 4, 5, 6,… The 4, 5, 6,… quark hadron degenerate multiplet masses follow by splitting of the heavy quark mass scales according to the spinorial decomposition of SU(2) × SU(2).     

Spectra, energy levels, and symmetry assignments for Stark components of Eu(4f) in gadolinium gallium garnet (Gd3Ga5O12)

Absorption and fluorescence spectra observed between 450 and 750 nm at 85 K and room temperature (300 K) are reported for Eu³⁺(4f⁶) in single-crystal Czochralski-grown garnet, Gd₃Ga₅O₁₂ (GGG). The spectra represent transitions between the ^2S+1L_J multiplets of the 4f⁶ electronic configuration of Eu³⁺ split by the crystal field of the garnet. In absorption, Eu³⁺ transitions are observed from the ground state, ⁷F₀, and the first excited multiplet, ⁷F₁, to multiplet manifolds ⁵D₀, ⁵D₁, and ⁵D₂. The Stark splitting of the ⁷F_J multiplets (J=0-6) was determined by analyzing the fluorescence transitions from ⁵D₀, ⁵D₁, and ⁵D₂ to ⁷F_J. The Eu³⁺ ions replace Gd³⁺ ions in sites of D₂ symmetry in the lattice during crystal growth. Associated with each multiplet manifold are 2J+1 non-degenerate Stark levels characterized by one of four possible irreducible representations (irreps) assigned by an algorithm based on the selection rules for electric-dipole (ED) and magnetic-dipole (MD) transitions between Stark levels in D₂ symmetry. The quasi-doublet in ⁵D₁ was characterized by an analysis of the magneto-optical spectra obtained from the transitions observed between ⁵D₁ and ⁷F₁. A parameterized Hamiltonian defined to operate within the entire 4f⁶ electronic configuration of Eu³⁺ was used to model the experimental Stark levels and their irreps. The crystal-field parameters were determined through use of a Monte-Carlo method in which nine independent crystal-field parameters, were given random starting values and optimized using standard least-squares fitting between calculated and experimental levels. The final fitting standard deviation between 57 calculated-to-experimental Stark levels is 5.9 cm⁻¹. The choice of coordinate system, in which the nine are real and the crystal-field z-axis is parallel to the [0 0 1] crystal axis and perpendicular to the xy plane, is identical to the choice we used previously in analyzing the spectra of Er³⁺ and Ho³⁺ garnets.     

Quenching cross sections of the B3Π+(Ou+) v′ = 14 level of I2 by H2, CO,and CH4

In this work the deexcitation of the B³Π⁺(O_u⁺), v′ = 14 level of I₂ after pulsed laser excitation has been studied. The quenching cross sections by collisions with I₂, H₂, CO, and CH₄ have been measured. The experimental results are 190 ± 14, 2.5 ± 0.3, 15.1 ± 0.4, and 18.0 ± 0.6 Ų, respectively. These values are compatible (within 30%) with the semiempirical scaling law of proportionality with the product of polarizability and the square root of reduced mass.     

Dissociative photoionization of l-menthone: An experimental and theoretical study

The dissociative photoionization mechanism of l-menthone has been investigated with photoionization mass spectrometry using synchrotron radiation. The adiabatic ionization energy (IE) of l-menthone and the appearance energies (AE) of its major fragment ions C₉H₁₅O⁺, C₉H₁₇⁺, C₈H₁₆⁺, C₇H₁₁O⁺, C₆H₁₀O⁺, C₆H₉O⁺, C₅H₈O⁺, C₅H₁₀⁺, C₄H₆O⁺, C₅H₉⁺, C₄H₈⁺, C₄H₇⁺, C₃H₇⁺, C₃H₆⁺, C₂H₂O⁺, and CH₃⁺ are determined with their photoionization efficiency (PIE) spectra in the photon energy region of ∼8−15.5 eV. Breakdown diagrams identifying the major products are presented. Dissociative photoionization channels for formation of these fragment ions are proposed based on comparison of determined experimental appearance energies and energies predicted with the DFT calculations. According to our results, the experimental dissociation energies are in fair agreement with the theoretical values of the possible photodissociation channels of C₁₀H₁₈O.     

Structure and magnetotransport properties of the new quasi-two-dimensional molecular metal β″-(BEDT-TTF)4H3O[Fe(C2O4)3] · C6H4Cl2

The β″-(BEDT-TTF)₄A^I[M^III(C₂O₄)₃] · G(A^I=NH ₄ ⁺ , H₃O⁺, K⁺, Rb⁺; M^III=Fe, Cr; G = “guest” solvent molecule) family of layered molecular conductors with magnetic metal oxalate anions exhibits a pronounced dependence of the conducting properties on the type of neutral solvent molecules introduced into the complex anion layer. A new organic dichlorobenzene (C₆H₄Cl₂)-containing conductor of this family, namely, β″-(BEDT-TTF)₄H₃O[Fe(C₂O₄)₃] · C₆H₄Cl₂, is synthesized. The structure of the synthesized single crystals studied by X-ray diffraction is characterized by the following parameters: a = 10.421(1) Å, b= 19.991(2) Å, c= 35.441(3) Å, β = 92.87(1)°, V= 7374(1) ų, space groupC2/c, and Z = 4. In the temperature range 0.5&;2-300 K, the conductivity of the crystals is metallic without changing into a superconducting state. The magnetotransport properties of the crystals are examined in magnetic fields up to 17 T at T = 0.5 K. In fields higher than 10 T, Shubnikov-de Haas oscillations are detected, and the Fourier spectrum of these oscillations contains two frequencies with maximum amplitudes of about 80 and 375 T. The experimental results are compared with the related data obtained for other phases of this family. The possible structural mechanisms of the effect of a guest solvent molecule on the transport properties of the β″-(BEDT-TTF)₄A^I[M^III(C₂O₄)₃] · G crystals are analyzed.