A study of EXAFS associated with the Re LIII discontinuity in metal and some compounds

The authors have reanalysed the data on the EXAFS associated with the rhenium L_III absorption discontinuity in the metal and in some of its compounds, and have interpreted them in the light of the recent theory proposed by Lytle, Sayers and Stern. It has been shown that the α parameter of EXAFS is a measure of valency and that the metallic valency of rhenium is two.     

Determination of bond lengths in some compounds of rhenium from the x-ray LIII absorption discontinuity

The shapes and the fine structure of the x-ray L_III absorption discontinuity of rhenium have been studied in seven octahedral (K₂ReCl₆, K₂ReBr₆, (pyH)₂ReCl₆, (dipyH)₂ReCl₆, Re(dipy)Cl₄, K₃ReO₂(CN)₄ and ReO₃) and three tetrahedral (KReO₄, NH₄ReO₄ and NaReO₄) compounds. The bond lengths in these compounds have been determined by applying Levy’s theory to the data on the fine structure associated with the edge beyond the molecular orbital region.     

Chemical shifts of K X-Ray absorption edge of copper in oxides

The K absorption edges of copper in the metal, cuprous oxide and cupric oxide are presented. The extended fine structure has been recorded in all the three substances.     

Chemical shifts of the copper and cobalt K absorption discontinuities in some ternary compounds

The present paper reports the chemical shifts of the K X-ray absorption discontinuities of copper and cobalt in ternary compounds. Relationships between the chemical shifts ΔE of the discontinuities and the various bond parameters (C, E_g, and f_i) calculated from Levine's theory have been established. It is found that distinctly separate curves can be drawn for different valencies (Cu¹⁺ and Cu²⁺, Co²⁺ and Co³⁺) of the absorbing ions. Making use of Levine's method for calculating bond charges, the effective charges q on the absorbing ions have been evaluated. The dependence of ΔE on q has been confirmed.     

Combined Mössbauer and LIII-edge X-ray absorption study of mixed- valent EuPd2Si2 and EuNi2P2

The mean valence of Eu is determined by L_III-edge X-ray absorption (L_III-XA) and ¹⁵¹Eu Mössbauer isomer shift measurementd for the mixed-valent compounds EuPd₂Si₂ and EuNi₂P₂ in the temperature range from 1.7 to 300 K. For EuPd₂Si₂, the behaviour of the satellite line observed in the Mössbauer spectra was investigated in detail. From a comparison of the L_III-Xa and Mössbauer results obtained on identical samples the valence/isomer shift calibration problem as well as possible final-state effects in L_III-XA spectra are discussed.     

Photoinduced absorption in Trans-(CD)x; isotope energy shifts

Steady state photoinduced absorption in trans (CD)_x is reported for energies of 0.1–2.1 eV. All induced infrared active vibrations as well as the photoinduced electronic bands show an energy down shift compared to those of (CH)_x. The change in the induced vibrations spectrum is fully understood and it results from different bare-phonons in the two isotopes. The origin of the isotope shift observed in the electronic bands is discussed.     

Reflexion speculaire du rayonnement X continu au voisinage du seuil LIII du lanthane

The spectral distribution of continuous X radiation, specularly reflected in the vicinity of the La L_III edge, is determined for various glancing angles. An anomalous behaviour of reflectivity is revealed, associated with a maximum in the photoabsorption spectrum. A simple theoretical model accounts for the phenomenon.     

K/L, LIII/MIII and M/(N + O + P) ratios in pure E2 transitions

Accurate measurements have been performed on relative K, L, M and (N + O + P) internal conversion line intensities of some pure E2 transitions in nuclei in the rare-earth region. The results are compared with theoretical values obtained from the calculations by Rose, Sliv and Band, Hager and Seltzer and by Bhalla. Good agreement between experiment and theory is found for the K/L ratios, while the experimentally obtained L_III/M_III ratios are somewhat lower than predicted by theory.     

Shape and chemical shifts of the cobalt K-absorption discontinuity in some complexes

X-ray K-absorption edges of cobalt (II) in its three complexes with para-amino salicylic acid have been recorded. The coordination symmetries of the three complexes have been established on the basis of the shapes of the absorption discontinuities. The coordination symmetries of the three complexes have been established on the basis of the shapes of the absorption discontinuities. The chemical shifts have been determined, and these shifts are employed to determine the effective nuclear charge on the central atom due to its chemical combination and the percentage covalency of the metal ligand bonds. The results are discussed.     

Optical absorption of the VOH center in MgO

An optical absorption band which peaks at 2.21 eV at room temperature has been assigned to the V_OH center in MgO, a linear defect consisting of the array O⁺ [=] HO⁺, where only deviations from the normal site charge are shown. This band is very similar to that of the V⁻ center. The relative oscillator strengths of the transitions is estimated to be f(V_OH)/f(V⁻) = 0.70 ± 0.1.     

Knight shifts and magnetic susceptibilities of the intermetallic compounds CeCu4 and CeCu5

The magnetic susceptibility and Knight shift of the compounds CeCu₄ and CeCu₅ have been measured over the temperature ranges 80–800 and 140–400 K, respectively. The most important contributions to the magnetic susceptibility are the Curie-Weiss term, expressing the paramagnetism of the localized ?-electrons, and a temperature independent term, which have both been determined. The phenomenological exchange integral F_s? between the 4?-electron spins and conduction electron spins was found to be ?10.43× 10^?3 eV for CeCu₄ and 3.9 × 10^?3 eV for CeCu₅. A reversal in the sign of the s?? coupling for CeCu₅ is noted.     

Magnetic susceptibilities and knight shifts of the intermetallic compounds NdCu4 and NdCu5

The magnetic susceptibility and Knight shift of the intermetallic compounds NdCu₄ and NdCu₅ were investigated over the temperature range 80–850 K. The most important contributions to the magnetic susceptibility are the Curie-Weiss term, expressing the paramagnetism of the localized 4?-electrons, and a temperature independent term, both of which have been determined. The phenomenological quantity J_s? between the 4?-electron and conduction electron spins was found to be ?2.46.10^?3eV for NdCu₄ and 1.35.10^?3 eV for NdCu₅. A reversal in the sign of the s-? coupling for CeCu₅ was noted.     

Chemical shifts of X-ray K or L-absorption edges of solids

A very simple method for the calculation of the chemical shifts of X-ray K or L-absorption edges of metals when they undergo chemical combination, is proposed. It has been found that the major contribution to the chemical shifts comes from the change in the Fermi energy when the metal forms a compound. Fairly good agreement in the nature and the numerical magnitude of the chemical shifts between the observed and calculated values has been obtained.     

The shape and extended fine structure of the manganese K X-ray absorption discontinuity in its oxides

The shape and extended fine structure of the manganese K absorption discontinuity have been studied in the pure metal and in its four oxides. viz. MnO, Mn₃O₄, Mn₂O₃ ad MnO₂ using a bent crystal Cauchois type spectrograph of 40cm diameter. The shape of the main discontinuity for the oxides is discussed on the basis of molecular orbital theory. Our results show a complimentarity between the absorption spectra and the emission spectra obtained earlier by Tsutsumi et al. for some of these oxides. The extended X-ray absorption fine structure (EXAFS) is discussed in the light of the recent proposed by Lytle et al.     

多孔TiO2/Al/SiO2纳米复合结构的紫外光吸收特性研究

在SiO₂玻璃衬底上用脉冲激光沉积(PLD)技术，分别沉积Ti和Ti/Al膜，经电化学阳极氧化成功制备了多孔TiO₂/SiO₂和TiO₂/Al/SiO₂纳米复合结构. 其中TiO₂薄膜上的微孔阵列高度有序，分布均匀. 实验研究了Al过渡层对多孔TiO₂薄膜光吸收特性的影响. 结果表明：无Al过渡层的多孔TiO₂薄膜其紫外吸收峰在27     

多孔TiO2/Al/SiO2纳米复合结构的紫外光吸收特性研究

在SiO₂玻璃衬底上用脉冲激光沉积(PLD)技术,分别沉积Ti和Ti/Al膜,经电化学阳极氧化成功制备了多孔TiO₂/SiO₂和TiO₂/Al/SiO₂纳米复合结构. 其中TiO₂薄膜上的微孔阵列高度有序,分布均匀. 实验研究了Al过渡层对多孔TiO₂薄膜光吸收特性的影响. 结果表明：无Al过渡层的多孔TiO₂薄膜其紫外吸收峰在27 关键词： 2薄膜')" href="#">多孔TiO₂薄膜 阳极氧化 紫外光吸收     

Hydrogen absorption in CeFe2 and ThFe3

The effect of hydrogen absorption on the magnetic properties of CeFe₂ and ThFe₃ was studied by magnetization measurements and by the ⁵⁷Fe Mössbauer effect. In both cases an increase in the transition metal moment is observed. In CeFe₂ the long range periodicity of the crystal lattice is lost whereas in ThFe₃ a structural change occurs. Surprisingly, the magnetic anomaly observed in ThFe₃ around 250 K is still present in the hydride.     

Thermomodulation of the aluminum L2,3 absorption edge

Thermomodulation spectra were obtained near the Al L_2,3 edge in Al films, using synchrotron radiation. These spectra, temperature derivatives of the absorption coefficient, completely resolve the two spin-orbit components. A fit to the shape of one component shows that broadening of the Fermi function is the dominant mechanism for the temperature dependence one-electron or many-body absorption process, is needed near the region of the “spike”.