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1.
Co2+ and Ni2+ ions doped β-BaB2O4 nanopowders have been prepared by co-precipitation method and their structural properties are studied by spectroscopic techniques. Powder XRD data reveals that the crystal structure belongs to monoclinic and the average crystallite size is calculated. Optical absorption spectra data reveal octahedral site symmetry for Co2+ and Ni2+ ions. Crystal field (Dq) and inter-electron repulsion (B and C) parameters are evaluated for Co2+ doped β-BaB2O4 nanopowders as Dq=960, B=900 and C=3850 cm?1 and for Ni2+ doped β-BaB2O4 nanopowders, Dq=900, B=850 and C=3500 cm?1. FT-IR spectra showed the characteristic vibrational bands related to BO3 and BO4 molecules. Photoluminescence spectra contain the emission bands in ultraviolet and blue regions.  相似文献   

2.
Theoretical calculations on the fine, hyperfine and Zeeman (g-factor) parameters are reported for the X2Π and A2Σ+ states of FH+, ClH+ and BrH+. The fine-structure constants [spin–orbit (A), Λ-doubling (p, q) and spin–rotation constants (γ Π, γ Σ)] are evaluated up to second order (via SO/L couplings with several excited states) using a multireference configuration interaction (MRCI) method, a Breit–Pauli Hamiltonian and 6-311++(2d,2pd) basis sets. Hyperfine constants of magnetic and electric type [Frosch–Foley (a, b, c, d) and nuclear quadrupole (eQq 0, eQq 2)] are studied with density functional methods and various basis sets. Magnetic dipole moments (parameterized via g-factors) are calculated in second order like the fine structure constants. The situation is somewhat complex for X2Π since no less than five different gs have to be evaluated in second order. In general, our results are in good agreement with those reported in the literature, mostly limited to the ground state. Our calculations confirm that, at equilibrium, all second-order properties are dominated by the couplings between the electronic states X and A.  相似文献   

3.
1 INTRODUCTIONMetal ionelectrostaticinterationsarenumerousinchemicalsystemsandhavebeenstudiedextensively[1~ 15] .Specifically ,metal c  相似文献   

4.
Ion exchange techniques were used to substitute Cr3+ and Rh2+ ions for the sodium ions present in sodium-beta″-alumina single crystals. The optical absorption and fluorescence spectra were obtained and the fluorescence lifetimes measured for both types of samples. In each case the emission consisted of two bands having significantly different decay times. The temperature dependences of the fluorescence intensities and lifetimes were measured for these bands. The results are interpreted in terms of the energy level structures of these ions in different crystal field sites in this host lattice and the diffusion of ions in the conduction plane which changes these sites.  相似文献   

5.
6.
The compound FeSr2NdCu2O7+ (Fe1212) was successfully synthesized by solid-state reaction. X-ray diffraction data indicate that the sample is of single phase. Rietveld whole-pattern-fitting method was used to refine the crystal structure of samples prepared under different annealing conditions using the tetragonal system with space group P4/mmm. Magnetization measurements indicate that magnetic susceptibility changes with temperature in a Curie-type manner. Resistance measurements indicate that these samples have a semiconductor-like behavior. PACS 61.10.Nz; 74.72.Jt  相似文献   

7.
In order to improve pinning properties of bulk Bi2Sr2CaCu2O8+δ (Bi-2212) materials, samples of both pure Bi-2212 and Bi-2212 with carbon nanotubes embedded (CNTE Bi-2212) have been prepared by partial-melting processing. The preparation conditions are chosen so that a significant fraction of carbon nanotubes can be successfully embedded in the material, as indicated by thermogravimetric analysis. The microstructure and composition of non-superconducting second phases are found to be different in these two types of samples. By means of magneto-optical (MO) imaging, flux distributions in both types of samples are investigated up to T=77 K. The MO investigation reveals the propagation of a flux front in both pure and CNTE Bi-2212, showing that there is a strong coupling between grains (clusters) which enables the flow of inter-granular currents. This grain coupling persists in our field range of ±180 mT. In bulk non-textured ceramic high-Tc superconductors, the flux fronts caused by currents flowing through the entire sample are observed for the first time. Intra-granular current densities are obtained from the images as a function of grain size. The MO investigations have revealed the differences in the current densities caused by the presence of carbon nanotubes, showing that the carbon nanotubes are indeed functioning like columnar defects produced by heavy-ion irradiation. The increase of the flux penetration field is also a manifestation of the increase of the transport current density in the CNTE Bi-2212. The superconducting properties in our samples are very well reproducible.  相似文献   

8.

The present study presents a thorough theoretical analysis of the electronic structure and conformational preference of Schiff’s base ligand N,N-bis(2-hydroxybenzilidene)-2,4,6-trimethyl benzene-1,3-diamine (H2L) and its metal complexes with Zn2+, Cu2+ and Ag+ ions. This study aims to investigate the behavior of H2L and the binuclear Zn2+ complex (1) as fluorescent probes for the detection of metal ions (Zn2+, Cu2+ and Ag+) using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The six conformers of the H2L ligand were optimized using the B3LYP/6–311?+??+?G** level of theory, while the L?2-metal complexes were optimized by applying the B3LYP functional with the LANL2DZ/6–311?+??+?G** mixed basis set. The gas-phase and solvated Enol-cis isomer (E-cis) was found to be the most stable species. The absorption spectra of the E-cis isomer and its metal complexes were simulated using B3LYP, CAM-B3LYP, M06-2X and ωB97X functionals with a 6–311?+??+?G** basis set for C, O, N and H atoms and a LANL2DZ basis set for the metal ions (Zn2+, Cu2+ and Ag+). The computational results of the B3LYP functional were in excellent agreement with the experimental results. Hence, it was adopted for performing the emission calculations. The results indicated that metal complex (1) can act as a fluorescent chemosensor for the detection of Ag+ and Cu2+ ions through the mechanism of intermolecular charge transfer (ICT) and as a molecular switch “On–Off-On” via the replacement of Cu2+ by Ag+ ions, as proved experimentally.

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9.
Carbon sulfide cation(CS~+) plays a dominant role in some astrophysical atmosphere environments. In this work, the rovibrational transition lines are computed for the lowest three electronic states, in which the internally contracted multireference configuration interaction approach(MRCI) with Davison size-extensivity correction(+Q) is employed to calculate the potential curves and dipole moments, and then the vibrational energies and spectroscopic constants are extracted. The Frank–Condon factors are calculated for the bands of X~2~+Σ~+–A~2Π and X~2Σ~+–B~2Σ~+systems, and the band of X~2Σ~+–A~2Π is in good agreement with the available experimental results. Transition dipole moments and the radiative lifetimes of the low-lying three states are evaluated. The opacities of the CS~+ molecule are computed at different temperatures under the pressure of 100 atms. It is found that as temperature increases, the band systems associated with different transitions for the three states become dim because of the increased population on the vibrational states and excited electronic states at high temperature.  相似文献   

10.
研究了用双硫腙光度法结合多元线性回归技术直接分析水相中有毒重金属离子的方法.结果表明,在β-环糊精和非离子表面活性剂Triton X-100的存在下,金属离子-双硫腙配位体系具有更高的灵敏度和稳定性.使用多元线性回归技术,可以在多种干扰金属离子共存的条件下,不经萃取和化学分离直接分析4种常见的有毒重金属离子.  相似文献   

11.
Solid solutions, Bi2Sr2-x La x CuO6+ withx< 1.3 and Bi2Sr2-x La x CaCu2O8+ with probablyx<1.3 are reported. Both solid solutions show considerable nonlinear changes in the unit cell dimensions and a change in the modulation vector from 4.7b to 3.5b forx=0 andx=1.2, respectively. It is shown that Bi2Sr2-x La x CaCu2O8+ shows sometimes the absence of the 0.54 nm period alonga, whereas the modulation remains, suggesting both features not to be correlated. The investigation of the solid solution Bi2Sr2-x La x CaCu2O8+ with probablyx<1.3 are reported. Both solid solutions show considerable nonlinear changes in the unit cell dimensions and a change in the modulation vector from 4.7b to 3.5b forx=0 andx=1.2, respectively. It is shown that Bi2Sr2-x La x CaCu2O8+ is severly hampered by the presence of the n=0 structure in the reaction product when one starts with stoichiometric mixture. This can be overcome by adding extra Ca and heating directly just below the melting point. However addition of Ca to the mixture leads to changes in the solid solution range, because Ca can replace Sr.  相似文献   

12.
The First Negative bands of 12C16O+ and 13C16O+, in the spectral region 40 000–46 000 cm−1, have been photographed at a resolution sufficient to resolve the spin-doubled components. These data for 12C16O+, along with previously reported data of the same transitions, as well as microwave transitions of 12C16O+ in the ground state, have been explicitly included in a least-squares fit to determine the most precise set of molecular constants to date for the B2Σ+ and X2Σ+ states of 12C16O+. Furthermore, we report a rotational analysis of the First Negative bands of 13C16O+ for the first time. Several molecular constants characterizing 13C16O+ in the B2Σ+ and the X2Σ+ states, including spin-doubling parameters, have been determined.  相似文献   

13.
The water vapour line broadening and shifting for 97 lines in the ν1 + ν2 + ν3 band induced by hydrogen pressure are measured with Bruker IFS 125 HR FTIR spectrometer. The measurements were performed at room temperature, at the spectral resolution of 0.01 cm?1 and in a wide pressure range of H2. The calculations of the broadening γ and shift δ coefficients were performed in the semi-classical method framework with use of an effective vibrationally depended interaction potential. Two potential parameters were optimised to improve the quality of calculations. Good agreements with measured broadening coefficients were achieved. The comparison of calculated broadening coefficients γ with the previous measurements is discussed. The analytical expressions that reproduce these coefficients for rotational, ν2, ν1, and ν3 vibrational bands are presented.  相似文献   

14.
Using a flight-time-difference method we measured the energy distributions of H-H+ and H+-H+ fragment pairs arising from collisional dissociation of 10keV H 2 + ions incident on He. The distributions measured at an angle of 0.28° with respect to the beam direction have maxima at 4.3eV for H-H+ and at 8.7eV for H+-H+ in the center-of-mass frame. The sharp maximum of the angle distribution in the CM frame at right angles to the beam direction observed in experiments in which only protons are detected does not appear in this coincidence experiment. This supports an earlier assumption that this sharp maximum can be ascribed to dissociation by vibrational-rotational excitation.  相似文献   

15.
Substitution of Ge4+ in place of Cu in Tl0.85Cr0.15Sr2CaCu2?xGexO7?δ (x = 0–0.6) showed initial increase in zero critical temperature value, Tc zero from 98 K (x = 0) to 100 K (x = 0.1) and in the range of 85–86 K for x = 0.2–0.3. The slow decrease in Tc zero is unexpected as tetravalent Ge4+ substitution is expected to strongly reduce hole concentration in the samples and suppress Tc zero. Excess conductivity analyses of resistance versus temperature data based on Asmalazov–Larkin (AL) theory revealed that the substitution induced 2D-to-3D transition of fluctuation induced conductivity with the highest transition temperature, T2D3D observed at x = 0.1. FTIR spectroscopy analysis indicates Ge4+ substitution cause reduction in CuO2/GeO2 interplanar distance while our calculation based on Lawrence–Doniach model revealed highest superconducting coherence length, ξc(0) and interplanar coupling, J at x = 0.3. On the other hand, substitution of divalent Mg2+ for Ca2+ in (Tl0.5Pb0.5)(Sr1.8Yb0.2)(Ca1?yMgy)Cu2O7 (y = 0–1.0), which is not expected to directly vary hole concentration, surprisingly caused Tc zero to increase from 89.6 K (y = 0) to an optimum value of 95.9 K (y = 0.6) before decreasing with further increase in y. Excess conductivity analyses showed 2D-to-3D transition of fluctuation induced conductivity for all samples where the highest T2D3D was at y = 0.4. Similar calculation revealed highest values of ξc(0) and J also at y = 0.4. FTIR analysis of the samples indicates inequivalent Cu(1)O(2)Pb/Tl lengths and possible tilting of CuO2 plane as a result of Mg2+ substitution. The increased ξc(0) and J as a result of the Ge4+ and Mg2+ substitutions are suggested to contributed to sustenance of superconductivity above 80 K in the samples.  相似文献   

16.
The isotopic difference between the diamagnetic shielding of a positive muon (+) in + HBr and H2O and the analogous shielding of protons is computed from first principles in free space and in Br2 solution, using a self-consistent cellular cluster multiple scattering method (SC-CMS) for condensed matter and for the free molecules. The isotope shift of the chemical shift is at the + in these molecules dissolved in liquid Br2 is evaluated with the eigenfunctions and eigenvalues obtained using Ramsey's formalism. For HBr the computed chemical shifts is are comparable with experiment and with the calculations of Breskman and Kanofsky and of Williams, and the solvent effect has the correct sign and order of magnitude. For H2O, is has also the correct sign and order of magnitude when compared with +SR experiments.  相似文献   

17.
The quantum state-to-state calculations of the D + ND→N + D_2 reaction are performed on a potential energy surface of 4 A' state. The state-resolved integral and differential cross sections and product state distributions are calculated and discussed. It is found that the rotational distribution, rather than the vibrational distribution, of the product has an obvious inversion. Due to the fact that it is a small-impact-parameter collision, its product D_2 is mainly dominated by rebound mechanism, which can lead to backward scattering at low collision energy. As the collision energy increases, the forward scattering and sideward scattering begin to appear. In addition, the backward collision is also found to happen at high collision energy, through which we can know that both the rebound mechanism and stripping mechanism exist at high collision energy.  相似文献   

18.
The potential energy surfaces (PESs) for several electronic states involved in the reaction O+ (4S) + N2(X1Σ+) → NO+ (X1Σ +, v′) + N(4S) and the role of the ionic N2O+ intermediate have been investigated by ab initio calculations. The 4A″ PES, which correlates with the ground state educts, has a barrier of about 1 eV, and therefore at low collision energies the reaction cannot take place adiabatically on this surface. However, the spin-orbit coupling in the entrance channel allows the system to pass into the Renner-Teller system of the X2 Π electronic ground state of the N2O+ intermediate. The reaction then proceeds on these surfaces up to the region in the exit channel where a similar coupling allows it to reach the product quartet asymptote. At collision energies higher than about 1 eV, the reaction proceeds mainly on the adiabatic PES of the 4A″ state. The A2Σ+ state of N2O+ predissociates via a vibronic coupling with the B2Π state, and in bent structures via a spin-orbit coupling with the 4A″ component of the 4II state. The electronic structure of the B2Π state is found to be of crucial importance for the understanding of the reactive processes in low lying electronic states of N2O+.  相似文献   

19.
We report combined studies on the prototypical S(1D2) + H2 insertion reaction. Kinetics and crossed-beam experiments are performed in experimental conditions approaching the cold energy regime, yielding absolute rate coefficients down to 5.8 K and relative integral cross sections to collision energies as low as 0.68 meV. They are supported by quantum calculations on a potential energy surface treating long-range interactions accurately. All results are consistent and the excitation function behavior is explained in terms of the cumulative contribution of various partial waves.  相似文献   

20.
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