Structural studies of nanocrystalline SnO2 doped with antimony: XRD and Mössbauer spectroscopy

A series of Sb-doped SnO₂ samples, with doping levels 0, 3.1, 6.2, 11.9 and 14.0 at% Sb, has been hydrothermally prepared and characterized by X-ray powder diffraction. Diffraction lines were broadened, the line broadening being anisotropic. Both the line broadening and line anisotropy were dependent on the Sb doping level. The samples are tetragonal, space group P4₂/mnm and isostructural with TiO₂(rutile). Sb doping of SnO₂ causes the increase of unit-cell parameters. The structure of pure SnO₂ and of samples containing 6.2 and 11.9 at% Sb has been refined by the Rietveld method. Crystal structure indicated that both Sb³⁺ and Sb⁵⁺ are substituted for Sn⁴⁺ in the SnO₂ structure, Sb³⁺ being dominant for the investigated doped samples. The samples were also examined by ¹¹⁹Sn- and ¹²¹Sb-Mössbauer spectroscopy. Mössbauer spectroscopy confirmed the XRD results. Also, the values of the isomer shifts and quadrupole coupling constants indicated that the configuration around the Sb³⁺ site includes the presence of the stereochemically active lone pair electrons.     

KTiOPO4晶体全部电光系数的测量

用干涉法测量了KriOPO₄晶体的全部电光系数。结果为γ₁₃=7.9,γ₂₃=11.3,γ₃₃=22.7,γ₅₁=10.6,γ₄₂=6.2(×10^-10cm/V)。 关键词：     

Influence of B atom diameter on annealing recovery rates of superconducting transition temperatures in irradiated A-15 (A3B) compounds

Fast Sc⁺ ions from an isotope separator are excited selectively by Doppler tuned radiation from a high power ultraviolet extension of the beam-laser technique. The cascade-free determination of the lifetime of the ScII3d4pz³F⁰₂ level yielded the value 6.2 ± 0.2 ns.     

Ba nuclear resonance in YBa2Cu2Oy

The first observations of NMR and NQR of both isotopes¹³⁵Ba and¹³⁴Ba in isotopically enriched samples of YBa₂Cu₃O_y with oxygen concentrations y=6.0, 6.2, and 7.0 are described. The pure NQR frequencies and asymmetry parameter are in good agreement with theoretical predictions. The temperature dependence of the NQR frequency of Ba for y=7 is qualitatively similar to that for Cu(2) but much stronger. The temperature dependence of the longitudinal and transverse relaxation times opens new questions.     

Comment on measuring photoionization cross sections of excited atomic states

The results of the measured absolute photoionization cross section from the 7² P excited states of cesium are reported. The following values have been obtained: (6.2±0.5)×10⁻¹⁸ cm² and (8.8±1.6)×10⁻¹⁸ cm² for the levels 7² P _1/2 and 7² P _3/2, respectively.     

Isomer shift of the 6.2 keV nuclear transition of 181Ta in Cu3TaSe4

The isomer shift of the 6.2 keV nuclear transition of ¹⁸¹Ta in Cu₃TaSe₄ was investigated by nuclear gamma resonance spectroscopy. Relative to tantalum metal the isomer shift measured corresponds to + 32.64±0.03 mm sec^?1, which is about 17 mm sec^?1 larger than that of the isotypic Cu₃TaS₄. This is explained by the lower electronegativity of selenium as compared to sulphur.     

Observation of knight shifts in metallic tungsten and tantalum with the 6.2 keV181Ta Mössbauer resonance

Completely resolved Mössbauer spectra for the 6.2 keV¹⁸¹Ta transition were measured at R.T. in external magnetic field of 2.8 and 4.4 kOe for¹⁸¹Ta impurities in W- and Tametal respectively. A more precise mean value for theg-factor ratiog _9/2/g _7/2 of 1.797(3) was obtained. The magnetic moment of the 6.2 keV-state was determined to be +5.47 (2) n.m. From the hyperfine fields at the¹⁸¹Ta-nuclei in W a Knight-shift of 2(1)% and in Ta of 1.7(8)% was deduced. For the spectrum of the magnetically splitted Ta-metal absorber a reduced dispersion parameter of 2ξ=20(2) was measured, while the linewidth showed only a slight narrowing.     

Measurement and analysis of the ν2 bands of 14ND3 and 15ND3

The ν₂ fundamentals of ¹⁴ND₃ and ¹⁵ND₃ have been observed with sufficient resolution to resolve many of the individual P, Q, and R lines for both components of the inversion doublet. With the help of the observed intensity alterations assignments of many of the lines were made. A least-squares analysis was applied to determine the various vibration-rotation constants pertinent for these transitions. The ¹⁴N¹⁵N isotope shift is found to be ?6.2 cm^?1.     

Ground state and singlet excited state of laser dye DCM: Dipole moments and solvent induced spectral shifts

The solvent-induced shifts of the absorption and emission spectra of 4-dicyanomethylene-2-methyl-6-p-dimethyl-amino-styryl- 4H-pyran (DCM) have been studied in a variety of solvents. The absorption spectrum of its first singlet excited state has been determined in methanolic solution (λ_max=455nm , ϵ_max=6.2×10⁴ 1 mol^-1 cm^-1).     

Thermodynamic properties of Rb2ZnCl4 associated with three phase transitions

Transitions were observed by heat capacity measurements at 74.6 K, 195.2 K, and 303 K. They are a soft mode transition (ΔH_t = 30 J mol^?1, ΔS_t = 0.42 J K^?1 mol^?1), a first-order commensurate-incommensurate transition (ΔH_t = 6.2 J mol^?1ΔS_t = 0.032 J K^?1 mol^?1), and a second-order incommensurate-normal transition, respectively.     

Specific Features of the Structural State of Iron Ions in Iron-Containing Composites Irradiated by Fast Electrons

The present paper analyzes the valence-coordination state of iron atoms in polymer composite materials fabricated from polystyrene and iron-ore concentrates – magnetite and hematite – upon exposure to fast electrons with energy of 6.2 MeV and fluence of 10¹⁸ electrons/cm². Changes in the phase content and valence-coordination and magnetic states of iron atoms are established. After irradiation, the hematite phase is transformed into the magnetite phase with a predominance of Fe³⁺ ions with [FeO₄] coordination, and the magnetite phase forms the wüstite-type (FeO) phase in which Fe²⁺ ions are arranged in [FeO₆] coordination.     

Photoluminescence and excited state structure in Bi3+-doped Y2SiO5 single crystalline films

Single crystalline films of Bi-doped Y₂SiO₅ are studied at 4.2–350 K by the time-resolved luminescence methods under excitation in the 3.8–6.2 eV energy range. Ultraviolet luminescence of Y₂SiO₅:Bi (≈3.6 eV) is shown to arise from the radiative decay of the metastable and radiative minima of the triplet relaxed excited state (RES) of Bi³⁺ centers which are related to the ³P₀ and ³P₁ levels of a free Bi³⁺ ion, respectively. The lowest-energy excitation band of this emission, located at ≈4.5 eV, is assigned to the ¹S₀ → ³P₁ transitions of a free Bi³⁺ ion. The phenomenological model is proposed to describe the excited-state dynamics of Bi³⁺ centers in Y₂SiO₅:Bi, and parameters of the triplet RES are determined.     

Alternate technique for simultaneous measurement of photoionization cross-section of isotopes by TOF mass spectrometer

New measurements of photoionization cross-sections of the lithium isotopes are reported employing a Time of Flight (TOF) mass spectrometer in conjunction with an atomic beam apparatus. Using a two-step selective photoionization and saturation technique, we have simultaneously measured the photoionization cross-section of the 2p excited state of both the isotopes Li⁶ and Li⁷ as 15±2.5 Mb and 18 ±2.5 Mb where as the corresponding number densities have been determined as N₀≈5.3×10¹⁰ atoms/cm³ and N₀≈6.2×10¹¹ atoms/cm³ respectively.     

Behavior of natrolite zeolite and fluorapatite at high pressures in a water medium

The hysteresises (～0.3–0.4 GPa) of two transitions in natrolite at 0.9 and 1.45 GPa, considerable changes in the Raman spectra, and the appearance of very intense low-frequency mode at 75 cm^?1 in the overhydrated phase of high pressure of water medium up to 6.2 GPa are observed for the first time. The dependences of the band frequencies of this phase are nonlinear, due clearly to changes in the positions of H₂O in the channels. According to Raman data, fluorapatite placed together with natrolite in a water medium in a diamond anvil cell exhibits no transitions up to 6.2 GPa and displays linear pressure dependences of the band frequencies.     

The decay of127Cs

The decay of¹²⁷Cs (T _1/2=6.2 h) was investigated by means of a Ge(Li) spectrometer and a double-focusingβ-ray spectrometer. The decay scheme for¹²⁷Cs is presented including eight new levels. The spins and parities for¹²⁷Xe levels were determined. Based on the determination of the spins for the ground and first excited levels the spin 9/2 for the isomeric state of¹²⁷Xe was proposed. The relative cumulative yields of caesium isotopes from the spallation of natural cerium with 660 MeV protons are given.     

Isomer shift of the electrically split 6.2 keV nuclear transition of Ta181 in CuTaS3

The isomer shift of the 6.2 keV nuclear transition of Ta181 in CuTaS₃RAIN was investigated by nuclear gamma resonance spectroscopy. Relative to tantalum metal the isomer shift in CuTaS₃ corresponds to +37.95±0.1 mm/s. The z component of the electric field gradient at the nuclear site of Ta181 was found to be V_zz = (−1.29±0.01)·10¹⁸ v/cm². The close correlation between the isomer shift in CuTaS₃ and the electronegativity of the Ta-ligands is pointed out.     

Three-nucleon calculations without the explicit use of two-body potentials

Using as two-nucleon interaction input the ³S₁-³D₁ and ¹S₀ partial waves, the Faddeev equations are solved for the three-nucleon bound state. The ³S₁³D₁T-matrix is calculated from the Reid potential. Avoiding the usual potential fit, the ¹S₀T-matrix is directly continued off-shell and is constructed consistent with the ¹S₀ phase shift of elastic two-nucleon scattering. The off-shell part of the ¹S₀T-matrix is parametrized and with this parametrization the dependence of the three-nucleon bound-state properties is studied. As a result it is found that the binding energy varies only between 6.2 MeV and 6.8 MeV, while the minimum in the charge form factor for electron scattering from ³He lies between 12.9 fm^?2 and 18.7 fm^?2. The larger (smaller) ³He binding energy is accompanied by a ³He charge form factor whose minimum is at larger (smaller) momentum transfers.     

Thermal diffusivity of MORB-composition rocks to 15 GPa: implications for triggering of deep seismicity

We have measured the thermal diffusivity of eclogite and majorite with a model MORB composition at pressures of 3 and 15 GPa, respectively. Both phase assemblages show inverse dependences of their thermal diffusivities on temperature: D _eclogite=9(10)×10^?10+7(1)×10^?4/T(K) m ²/s and D _majorite=6.2(5)×10^?7+3.0(5)×10^?4/T(K) m ²/s. The values for majorite are in good agreement with previous measurements for other garnets and are considerably lower than thermal diffusivities of wadsleyite and ringwoodite, which are the main components of the mantle transition zone. We discuss the implications of the low thermal conductivity of subducted oceanic crust in the transition zone for the triggering of deep seismicity.     

A photoemission study (XPS and UPS) of the superconductor ErBa2Cu4O8 and comparison with YBa2Cu3O7-δ(δ≈0,1)

Core level and valence band photoemission spectra of the 124 superconductor ErBa₂Cu₄O₈ are investigated using MgK , HeI, and HeII radiation and compared with photoemission spectra of orthorhombic YBa₂Cu₃O₇ and tetragonal YBa₂Cu₃O_6.2 samples. It is found that the Cu 2p _3/2 core level and the UPS valence band spectra of ErBa₂Cu₄O₈ and YBa₂Cu₃O₇ are very similar but differ significantly from those of YBa₂Cu₃O_6.2. From the resemblance between the ErBa₂Cu₄O₈ and YBa₂Cu₃O₇ spectra it follows that the electronic structures of these two compounds are closely related in spite of an additional CuO chain in the 124 phase. The differences between the YBa₂Cu₃O_6.2 spectra and the other spectra are explained by the the presence of monovalent copper at the crystallographic Cu(1) sites. The Cu 2p _3/2 lineshapes of the here studied superconductors and some Cu^II compounds are discussed.     

Interaction of neutrons with zinc and its isotopes

Coherent neutron scattering lengths and total cross sections have been measured for elemental Zn,Zn-compounds and on isotopicly enriched samples for neutron energies from 0.5 meV up to 143 keV using different techniques. From the experimental data the following quantities were obtained:

the coherent scattering lengths (b in fm) of Zn (5.689±0.014);⁶⁴Zn (5.23±0.04);⁶⁶Zn (5.98±0.05);⁶⁷Zn (7.58±0.08;b ₊=9.4±0.5/5.8±0.5;b _?=5.0±0.7/10.1±0.7);⁶⁸Zn (6.04 ±0.03);

the potential scattering radii (R′ in fm) of Zn (6.2±0.2),⁶⁴Zn (6.0±0.3) and⁶⁶Zn (6.2 ±0.3);

the absorption cross sections (σ _γ at 0.025 eV in barn) of Zn (1.11±0.02);⁶⁴Zn (1.1 ±0.1) and⁶⁶Zn (0.62±0.06).

Derived quantities are the “zero energy” scattering cross sections (σ ₀ in barn) for Zn (4.128±0.010) and⁶⁷Zn (7.8±0.3) and the incoherent bound cross sections of Zn (0.061 ±0.023) and⁶⁷Zn (0.6±0.4). In the epithermal region the Zn-cross section can be described by introduction of two strong bound levels of⁶⁷Zn+n for which estimated parameters are given.