Relaxation phenomena involved in the L3M4,5M4,5;1G4 auger process in zinc metal

A detailed analysis is presented of the L₃M_4,5M_4,5;¹G₄ Auger transition in metallic zinc. An extra-atomic relaxation term, neglected until now, is taken into account. This results in excellent agreement between calculated and experimental values of the Auger-transition energy.     

Detailed analysis of the L3M4,5M4,5; 1G4 Auger transition in atomic zinc: Improved Auger energy calculations

A hitherto neglected relaxation term is introduced in the calculation of Auger electron energies. The agreement between the theoretical L₃M_4,5M_4,5; ¹G₄ Auger energy in atomic zinc and the experimental value of Aksela and Aksela is excellent. Relaxation energies are determined by means of OHFS hole state calculations.     

X-ray photoelectron emission studies of mixed selenides AgGaSe2 and Ag9GaSe6

Auger and direct electron specta from crystalline AgGaSe₂ and Ag₉GaSe₆ have been studied with X-ray photoelectron spectroscopy. It is shown that the AgM₅N_4,5N_4,5 and M₄N_4,5N_4,5 Auger spectra are more sensitive to the chemical environment than the Ag 3d direct photoelectron spectra. Furthermore the Auger parameter as defined by Wagner is used in order to characterize the chemical state of these compounds. Last, the XPS spectra of the valence-band region are investigated and chalcogen s and p and noble-metal d bands are clearly identified. The electronic structure of these two selenides does not seem to be determined predominantly by the crystal structure. As a whole, the spectral features are discussed in connection with the character of the chemical bonding and the physical properties of these compounds.     

Die Kristallstruktur des Calciumhydrogensulfat-Dihydrogensulfats – ein neuer Strukturtyp für schwefelsaure Hydrogensulfate

Extra-atomic Relaxation Energy — a New Physical Parameter Characterizing Chemical Bonding A new method is proposed for the determination of extra-atomic relaxation in chemical compounds. The extra-atomic relaxation is obtained as the difference between experimental and theoretical Auger parameters. The extra-atomic relaxation energy characterizes the chemical bondings ionicity of the atom under consideration with his surrounding atoms. The calculated extra-atomic relaxations are the additive function of the ligands of the atom studied. The increments of the additive scheme correlate with the ligand refraction. The method has been applied to solid compounds of the elements from Na to Cl, and to a number of free sulfur-, phosphorus-, silicon-and chlorinecontaining molecules. The obtained extra-atomic relaxation energies agree well with both calculated and direct experimental results. The application of the extra-atomic relaxation for determination of the effective atomic charge in hypothetical compounds is demonstrated for ArO₄.     

Titanocene complexes of the N-methyl and N-phenyl-1,3-thiazoline-2-thione-4,5-dithiolates and 4,5-diselenolate ligands

Cp₂Ti(dithiolene) and Cp₂Ti(diselenolene) complexes containing the N-methyl-1,3-thiazoline-2-thione-4,5-dithiolate ligand (Me-thiazdt), the N-phenyl-1,3-thiazoline-2-thione-4,5-dithiolate ligand (Ph-thiazdt) and the N-methyl-1,3-thiazoline-2-thione-4,5-diselenolate ligand (Me-thiazds) have been synthesized. Three approaches have been developed in order to generate the dithiolene or the diselenolene ligands which were reacted with Cp₂TiCl₂ to form the corresponding heteroleptic complexes. Their X-ray crystal structures, UV-Vis absorption spectra as well as their redox properties, determined by cyclic voltammetry have been investigated and discussed. Variable-temperature ¹H NMR experiments have been performed in order to determine the activation energies of the chelate ring inversion.     

SCF Xα SW calculations of chemical shifts of X-ray and electron emission lines and relaxation properties of SiX4 molecules

SCF Xα SW calculations of the 1s and 2p binding energies, KLL Auger energies and Kα transition energies for the molecules SiH₄, SiCl₄ and SiF₄ and the corresponding atomic Xα calculations for charged free silicon ions have been carried out. The results provide information about relaxation properties and anomalous chemical Kα shifts in hydrides.     

Binding and L23MM auger energies in atomic and metallic zinc

An analysis of the photoelectron and photon-induced L₂₃MM Auger spectra of Zn metal has been performed. The relaxation processes involved in the Auger transitions have been investigated. They account well for the experimental Auger energies.     

Gas phase electron diffraction study of SiH3N3 and (SiH3)2 NCN

The molecular structures of SiH₃N₃ and (SiH₃)₂ NCN have been determined by electron diffraction : SiH₃N₃ has a non-linear SiN₃ skeleton, and (SiH₃)₂ NCN is a carbodiimide with SiNCN Si probably linear. A new model is proposed which rationalises the observed geometry of a number of molecular pseudohalides.     

Ionization energies and electronic structure of N3P3Cl6 as determined by UV photoelectron spectroscopy and the Xα scattered wave method

Ionization energies have been measured for N₃P₃Cl₆ by He I photoelectron spectroscopy and they are compared with values calculated with the overlapping-spheres version of the Xα scattered wave method; the average discrepancy is less than 0.4 eV. The wavefunctions and associated charge distributions are used for assessing models of ring π bonding, and comparisons are made with previous calculations for N₃P₃F₆ and N₄P₄F₈. The calculated charge distributions are related to trends in measured core electron binding energies, and have important implications for the interpretation of Faraday effect measurements on cyclic phosphazenes.     

The relevancy of the [B2N4] substructure in the electronic structure of the metal-rich lanthanum nitridoborate La3(B2N4)

Lanthanoide nitridoborates of the general formula Ln₃(B₂N₄) with Ln=La, Ce, Pr, and Nd occur as black crystalline materials. Their structures contain oxalate-like [B₂N₄]⁸⁻ ions being stacked in an eclipsed formation along one crystallographic direction. Electronic structures were calculated for a molecular [B₂N₄]⁸⁻, for the [B₂N₄] partial structure, and for the complete La₃(B₂N₄) structure with the extended Hückel algorithm to analyze the bonding characteristics and to trace the necessity and properties of one surplus electron of (La³⁺)₃(B₂N₄⁸⁻)(e⁻). The HOMO of a [B₂N₄]⁸⁻ is B-B σ bonding, and the LUMO is B-B π bonding but B-N antibonding. The energy band of the solid state [B₂N₄] partial structure corresponding to the LUMO is broadened as a result of intermolecular B?B interactions between adjacent [B₂N₄] units along the stacking direction. Due to bonding interactions with La d orbitals, this band is significantly lowered in energy and occupied with one electron in the band structure of La₃(B₂N₄). This singly occupied band exhibits no band crossings but creates a semimetal-like band structure situation.     

Vibrational Spectra of the Cyclic SN-Compounds S4N4, S4N4H4 and S3N3Cl3

The IR and Raman spectra of solid and dissolved S₄N₄, S₄N₄H₄, S₄N₄D₄ and S₃N₃Cl₃ have been recorded and are assigned according to D_2d, C_4v and C_3v symmetry respectively. In the solid state, many forbidden bands and splittings of degenerate vibrations are observed because of the symmetry lowering in the crystals. Due to the different size and shape of the rings and to strong coupling of the normal modes there is no clear correlation between the SN ring stretching vibrations and the strength of the SN bonds, except for the one of the E modes. However, the stretching force constant show the trend expected from changes in interatomic distances.     

Combined bulk and surface analysis of oxygen species in Si3N4 powders by means of carrier-gas heat-extraction methods and Auger electron spectrometry

Summary By means of the addition of 1%(v/v) C₂H₄ to He carrier gas and by application of a temperature ramp starting from 100°C in the carrier-gas heat-extraction technique, discrimination between two siloxane species in Si₃N₄ is feasible. By comparison with Auger electron spectrometry data, one species can be assigned to the surface and the other to bulk siloxane. This is demonstrated by means of two differently manufactured Si₃N₄ powders which are HF-etched or oxidized so that their — predominantly near-surface — oxygen content is decreased or increased, respectively. Additional oxygen speciation can be achieved by means of thermo-desorption of oxygen bound to hydrogen and carbon in Ar between room temperature and about 1000°C.     

B12N12 Nano-cage as Potential Sensor for NO2 Detection

The NO₂ molecule adsorption on B₁₂N₁₂ nano-cage was investigated using density func-tional theory calculations in terms of adsorption energy, HOMO/LUMO energy gap (Eg) changes, charge transfer, structural deformation, etc. Furthermore, some aspects of stability and properties of B₁₂N₁₂ including calculation of binding electronic and Gibbs free energies, density of states, and molecular electrostatic potential surfaces are investigated. Three pos-sible configurations for NO₂ adsorption on the B₁₂N₁₂ nano-cage are energetically found. Interestingly, the results reveals that the Eg of B₁₂N₁₂ cluster is very sensitive to the pres-ence of NO₂ molecules as its value reduces from 6.84 eV in free cluster to 3.23 eV in the most stable configuration of NO₂/cluster complex. This phenomenon dramatically increases the electrical conductivity of the cluster, suggesting that the B₁₂N₁₂ nano-cluster may be potential sensor for NO₂ gaseous molecule detection.     

Calculation of sulphur L(S2p)-MM Auger energies of H2S

The Auger energies of the L(S2p)-MM transitions of H₂S have been computed using MC SCF methods. The results are sufficiently accurate to assign the experimental spectrum and indicate large relaxation as well as large single-triplet splitting for low energy transitions.     

Chemical shifts of auger electron lines and electron binding energies in free molecules. Sulfur compounds

The first paper describing a series of systematic investigations of the chemical shifts in Auger electron spectra from various free molecules is presented. Excitation is performed by means of a fine focus electron beam. The Auger electrons are retarded in a four component lens system and recorded at high resolution in a new multidetector system placed in the focal plane of the ESCA instrument. A calibration procedure against the KL₂L₃ Auger electron line of Ne is described. The first study concerns Auger electron line shifts for sulfur in some small molecules and the results are compared to the corresponding chemical shifts in the core photoelectron spectra. A formalism based on a transition potential model is briefly presented which takes account of the relaxation energies involved in Auger transitions as well as in single photoionization.     

激光CVD法合成SiC-Si3N4复合纳米颗粒

用激光化学蒸汽沉积(CVD)法合成了SiC-Si₃N₄复合纳米颗粒,并用X射线衍射(XRD),透射电子显微镜(TEM)和电子自旋共振磁力计(ESR)分析了试料的晶体结构,颗粒形状以及悬空键的状况。合成的试料粒度分布集中,平均粒径为32nm,颗粒由直径为5～30nm的单晶或多晶组成。试料纯度高,颗粒为近似球形,十分适合于粉体的加工和烧结。另外试料有很高的热稳定性,在加热的过程中的变化首先是悬空键减少,然后是相分解和颗粒长大。     

Double electron transfer reactions of CO22+ ions

Time-of-flight techniques have been used to measure fast neutral CO₂ products from double electron transfer reactions of CO₂²⁺ ions with 4.0–7.0 keV impact energies. Double electron transfer cross sections have been determined to be in the range of (1.1–12.5) × 10^?16 cm² for reactions of CO₂²⁺ ions with CO₂, CO, N₂, Ar and O₂.     

Differential cross section for CN− formation from dissociative electron attachment to the cyanogen molecule C2N2

The differential cross section for CN^? formaition from dissoiiativc attachment on C₂N₂ has been obtained in a crossed-beam experiment. Below 10 eV incident electron energy thc CN^? cross section shows two broad overlapping peaks with maxima at 5.4 and 7.3 eV corresponding to the formation of CN^? in its ground electronic state ¹σ⁺ plus the CN radical in the first excited state²π and the ground stale ²Σ+ respcctively     

Bromine NQR study of structure and molecular torsional motion in N4P4Br8 and N3P3Br6

The bromine NQR spectrum of tetrameric bromocyclophosphazene, N₄P₄Br₈, has been studied in the temperature range from 77 to 300 K. The negative temperature coefficients of the resonance frequencies have been analysed using Bayer-Kushida-Brown equations. Torsional modes in the frequency range 10–15 cm^?1 are shown to characterise the observed motional averaging and are only slightly temperature dependent. The multiplicity and relative intensities of resonances in the trimer, N₃P₃Br₆, have been correlated with the known electron density distribution. The results for the bromo-derivatives are compared with those reported for the corresponding chloro-derivatives.     

Pt/g-C3N4/KB纳米复合催化剂的制备及其甲醇氧化性能

采用溶液中等离子放电法制备出了Pt纳米颗粒,用热氧化刻蚀和水热法成功的对石墨相氮化碳（g-C₃N₄）进行处理进而均匀吸附在科琴黑（KB）表面,最终制备出了Pt/g-C₃N₄/KB纳米复合催化剂。通过XRD分析,扫描电镜,透射电镜和电化学工作站探究了催化剂的组成、结构、颗粒大小以及电化学性能。Pt/g-C₃N₄/KB纳米复合催化剂展现出了良好的甲醇电氧化性能,性能的提升可能是由于g-C₃N₄良好的化学稳定性,N元素的存在改变Pt外层电子结构从而提高催化活性,这些因素提高了Pt的催化效率。