Electronic structure of the octachlorodimolybdenum(II) anion using X-ray emission and X-ray photoelectron spectroscopies

X-ray emission (Mo Lβ_{2, 15} and Cl Kβ_{1, 3}) and X-ray photoelectron spectra from K₄ [Mo₂ Cl₈] have been combined to give a detailed picture of the electronic structure of the octachlorodimolybdenum(II) anion. Chlorine 3p orbitals form a relatively narrow band which has the same range of ionization energies as the more tightly bound orbitals with molybdenum 4d character. The molecular orbitals of the MoMo quadruple bond can be identified as well as those involved in MoCl bond formation and Cl non-bonding orbitals.     

A four-component Fock-space coupled cluster investigation of the HM(CO)5, (M = Mn,Re) photoelectron spectra

In this work, we readdress the photoelectron spectra of the HM(CO)₅, (M=Mn, Re) carbonyl complexes by applying four-component Fock-space coupled cluster (FSCC) methods for their calculation in order to extend earlier studies based on less demanding approaches. The final-state characterisation was based on group theoretical considerations of the contributing orbitals and allowed for an unambiguous assignment. Energy level diagrams show the effect of spin–orbit (SO) coupling starting from scalar relativistic results and for the heavy representative HRe(CO)₅ nonadditivity effects of SO and electron correlation can be observed requiring a consistent treatment of both contributions.     

过渡金属羰基化合物Mn(CO)5Br和Re(CO)5Br结构与动力学的超快光谱

利用超快泵浦探测红外光谱、稳态线性红外光谱和计算化学方法,对过渡金属羰基化合物Mn(CO)₅Br和Re(CO)₅Br的振动和结构动力学进行了研究. 借助羰基的两个伸缩振动峰(处于低频的A₁模式和处于高频的简并E模式)进行了观测. 结果表明,在两个配合物中,A₁和E模式振动峰的振动频率位置及频率差都与中心金属原子对羰基的键级和振动力常数的影响相关. 而A₁模式比E模式的线宽宽一些,部分由于振动寿命的影响. 此外,从瞬态光谱中获得了振动模式依赖的对角非谐性常数,发现在两个羰基化合物中E模式的非谐性总是较小.     

Structural, magnetic and electronic structure studies of Mn doped TiO2 thin films

We report structural, magnetic and electronic structure study of Mn doped TiO₂ thin films grown using pulsed laser deposition method. The films were characterized using X-ray diffraction (XRD), dc magnetization, X-ray magnetic circular dichroism (XMCD) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy measurements. XRD results indicate that films exhibit single phase nature with rutile structure and exclude the secondary phase related to Mn metal cluster or any oxide phase of Mn. Magnetization studies reveal that both the films (3% and 5% Mn doped TiO₂) exhibit room temperature ferromagnetism and saturation magnetization increases with increase in concentration of Mn doping. The spectral features of XMCD at Mn L_3,2 edge show that Mn²⁺ ions contribute to the ferromagnetism. NEXAFS spectra measured at O K edge show a strong hybridization between Mn, Ti 3d and O 2p orbitals. NEXAFS spectra measured at Mn and Ti L_3,2 edge show that Mn exist in +2 valence state, whereas, Ti is in +4 state in Mn doped TiO₂ films.     

X-Ray spectral and theoretical investigations of the electronic structure of phenylcyclosilanes (SiPh2) n (n = 4–6)

The X-ray emission SiKα_{1, 2} and SiKβ₁ spectra of a series of phenylcyclosilanes (SiPh₂) _n (n = 4–6) have been obtained. Using the results of quantum-chemical calculations in the density functional theory approximation, the fine structure of SiKβ₁ spectra has been interpreted. Distributions of densities of electron states of silicon atoms over the valence band have been constructed and the types of chemical bonds providing the Si-Si and Si-Ph interactions have been established. Based on the theory of natural bond orbitals, the chemical bonding in the studied series of phenylcyclosilanes has been analyzed.     

Electronic structure of SiO<Subscript>2</Subscript>: An X-ray emission spectroscopic and density functional theoretical study

The electronic structure of SiO₂ is investigated by means of valence to core X-ray emission spectroscopy and quantum-mechanical calculations in the density functional theory approximation. Analysis of a complete set of SiK_α1, SiL_{2, 3}, and OKα X-ray emission and XPS spectra along with the calculated data provides comprehensive information on chemical interactions that occur in SiO₂.     

X-ray emission spectra and electronic structure of Mn impurities in diluted Al,Ni and Cu-based solid solutions

Mn L_α emission spectra of pure metal and AlMn, CuMn and NiMn alloys are presented. For CuMn and NiMn alloys, the dependence of the width of structureless emission band on Mn concentration is discussed. For Al_0.995Mn_0.005 alloy, distoted shape of the emission spectrum reveals the spin splitting of impurity virtual bound states.     

X-ray emission spectra and electronic structure of VO,VN, VC

The experimental K_β5 and L_α emission spectra for vanadium and K_α spectra for nonmetal are studied for vanadium monoxide, nitride and carbide. Using the spectra unfolding the experimental molecular orbital diagrams have been obtained. By the semiempirical Mulliken-Wolfsberg-Helmholz method with the self-consistency on charges and configurations the calculations of electronic structure of clusters [VO₆]^10?, [VN₆]^15? and [VC₆]^20? have been carried out. The results of calculations are compared with the X-ray data. The effects of chemical bonding and charge densities on metal atoms in VO, VN, VC are discussed.     

Valence state of manganese ions in the La1−α BiLaβMnLa1−δ OLa3±γ ceramics

The valence state of the Mn ions in ceramic samples of the La_1?α BiLa_βMnLa_1?δ OLa_3±γ composition (LBMO) has been studied using the X-ray photoelectron spectroscopy. The presence of Mn³⁺ and Mn⁴⁺ ions in these compounds has been shown. The relative content Mn³⁺/Mn⁴⁺ has been determined by means of fitting the experimental Mn 2p spectra by the superposition of theoretical spectra of Mn³⁺ and Mn⁴⁺ ions. The elemental composition of the samples has been determined by the X-ray photoelectron spectroscopy and electron probe microanalysis. It has been established that the relative content of Mn⁴⁺ ions correlates with parameter δ, which characterizes the deviation of the actual elemental composition of the La_1?α BiLa_βMnLa_1?δ OLa_3±γ ceramics from stoichiometry La_{1 ? x} Bi _x MnO₃.     

Thermal phase transition of RbMnFe(CN)6 observed by X-ray emission and absorption spectroscopy

The thermal phase transition of RbMnFe(CN)₆ has been observed by Mn and Fe 3p-1s X-ray emission spectroscopy (XES) and 1s X-ray absorption spectroscopy (XAS). The thermal variations of the spin states and the valences of Mn and Fe were determined to be Mn²⁺(S=5/2)-NC-Fe³⁺(S=1/2) for the high-temperature (HT) phase and Mn³⁺(S=2)-NC-Fe²⁺(S=0) for the low-temperature (LT) phase. These transitions are thus caused by charge transfer between Mn and Fe. The temperature dependences of Mn and Fe 3p-1s XES and 1s XAS were observed as the composition of the spectra of the HT and LT phases. The ratios of the HT component in each spectrum show good agreement with the thermal transition curves observed with magnetic susceptibility measurements.     

Local structure of Mn in (Ga,Mn)As probed by X-ray absorption spectroscopy

Local structure of Mn atoms in Ga_1−xMn_xAs epilayers was studied using the X-ray absorption fine structure (XAFS) at Mn K-edge. X-ray near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) techniques were used. XAFS spectra for different Mn sites has been calculated and compared with the experimental data. Multi-parameter fitting of the EXAFS data indicates that 15-25% of Mn atoms are in interstitial sites in the as grown films. The Mn-As bond length has been found longer than Ga-As bond length in GaAs for both substitutional (Mn_Ga) and interstitial (Mn_I) sites.     

Electronic structure of 3d-metal monosulphides by the xα discrete variational method

Electronic structure calculations of MS^10?₆ clusters (M = Mn, Fe, Co, Ni) have been performed making use of the X_α discrete variational method. The results of the calculations are used for the detailed interpretation of the X-ray emission and photoelectron spectra for Mn, Fe, Co and Ni monosulphides and in a discussion of the physical-chemical properties of the compounds under investigation.     

Relation between 2p X-ray photoelectron and Kα X-ray emission spectra of manganese and iron oxides

The high resolution Mn and Fe Kα X-ray emission spectra (XES), and Mn and Fe 2p X-ray photoelectron spectra (XPS) for manganese and iron oxides were measured. The spectra were compared with those of [MnO₄]⁻, [Fe(CN)₆]⁴⁻ and [Fe(CN)₆]³⁻ ions. As the electronic structure of the latter compounds do not change with electron hole creation in the core levels, satellite peaks due to charge transfer are not observed in the 2p XPS spectra, and the peak profiles of metal 2p XPS and Kα XES are governed by the exchange splitting between 2p and valence electrons. The metal 2p XPS spectra of the oxides had satellite peaks, but the XES spectra had no satellites. FWHMs of the metal 2p_3/2 main peaks of the compounds being low spin states are smaller than those of metal Kα₁ XES spectra. However, FWHMs of Mn 2p_3/2 of the manganese oxide were nearly equal to those of Mn Kα₁ XES spectra, and those of Fe 2p_3/2 XPS spectra of the iron oxides are greater than those of Fe Kα₁ XES spectra.     

A study of some potassium hexachlorometallate complexes using electron spectroscopy

X-ray photoelectron (ESCA) spectra of the core (Cl 2p K 2p and metal 4f, if present) and valence orbitals are reported for K₂ReCl₆, K₂OsCl₆, K₂IrCl₆· 3 H₂O, K₂PtCl₆, K₃MoCl₆, and K₂SnCl₆. The K 2p_{$\text{3}\text{2}$} binding energy was found to be nearly constant (292.7 eV) and that of Cl to increase very slightly with increasing atomic number for the third row transition metals. The chemical shifts of Re(IV), Os(IV), Ir(IV), and Pt(IV) relative to the metals were in qualitative agreement with atomic calculations utilizing configurations obtained from extended Hückel calculations. The valence spectra of the transition metal complexes exhibit a three-band structure. On the basis of MO results and intensity considerations the high binding energy band is assigned as a composite of the a_1g, e_g, 1t_2g MO's. The middle band represents the t_2u, 2t_1g MO's; and the low binding energy band the 2t_2g MO. Calculated nd orbital photoionization cross sections correlate reasonably well with the relative intensifies of the valence manifolds. Comparison of band separations and charge-transfer transition energies suggests that interelectronic repulsion and MO energy separation contribute about equally to the overall charge-transfer energy.     

An interpretation of the Auger LVV transitions from oxides of third-row elements

The principal features in the LVV Auger spectra from the oxides of third-row elements are semi-empirically derived for the XO₄^n? species of Si, PS and Cl, and the XO₆^n? species of Mg and Al. Electron molecular orbital energies are derived from X-ray photoelectron and X-ray emission spectra; the central atom 3p electron density of states is taken from the Kβ X-ray emission. Two principal peaks, separated by ca. 14 eV, are predicted for the central atom LVV Auger spectra and are experimentally confirmed for the XO₄^n? species. Similar features are observed in published spectra for oxides of Mg and Al. These peaks correspond to central atom 3p electrons in orbitals whose energy is dominated by the atomic oxygen 2s and 2p electron levels. An examination of the total LVV line-shape shows that a self-convolution of the Kβ spectra does not reproduce the more subtle features, which are probably a result of the contributions of other electron orbitals and final-state effects. The possibility of using the LVV Auger spectra to discriminate between various oxide stoichiometries, i.e. sulfate, sulfite, etc., and between various ligand species, i.e. carbide, nitride, oxide, fluoride, is discussed.     

Carbon-13 NMR Spectra of Some Group VIIB Transition Metal Thiocarbonyl and Selenocarbonyl Complexes

Recently, we reported the discovery of the first examples of transition metal selenocarbonyl complexes, (n⁵-C₅H₅) Mn (CO)₂ (CSe) and (n⁶-C₆H₅CO₂CH₂(CO)₂ (CSe).¹ These complexes are particularly interesting because, unlike CO and CS, the diatomic CSe molecule has so far eluded isolation even at very low temperatures,² and so these complexes represent the stabilization of a chemically unstable species through coordination to a metal (cf. metal carbene complexes). We have also synthesized several thiocarbonyl complexes of the same type,^3,4 as well as the analogous rhenium selenocarbonyl complexes.⁴ While many detailed studies of the ¹³C nmr spectra of transition metal carbonyls have appeared in the literature over the past few years, there have been no such studies for the closely related thiocarbonyls and selenocarbonyls, although a few isolated data have been reported recently for metal thiocarbonyls.^5,6 In this communication, we report the ¹³C nmr spectra of the isoelectronic series of complexes, (n⁵-C₅H₄R) M(COI)₂ (CX) (M = Mn, R = H, CH₃; M = Re, R = H; X = O,S, Se).     

Inner shell excitation of CH 3F,CH 3Cl,CH 3Br and CH 3I by 2.5 keV electron impact

Small angle inelastic scattering of 2.5 keV electrons was used to study inner shell excitation in the methyl halides at energy transfers between 50 and 700 eV. Discrete peaks due to the excitation of carbon K, fluorine K, chlorine L, bromine M_{4, 5} and iodine N _{4, 5} electrons were observed. Correlations through the methyl halide series were used to aid in the assignment of features in the carbon K-shell spectra. A comparison of halogen inner-shell excitation structures with the carbon K-shell excitation structure in the same molecule allowed a complete assignment of all spectral features. The assignments proposed involve promotions of inner shell electrons to unoccupied valence and Rydberg orbitals. On the basis of our assignments of the chlorine L- and carbon K-shell electron energy loss spectra of CH ₃Cl we propose an alternate assignment of the previously reported CH ₃Cl chlorine K-shell photoabsorption spectrum.     

Ultraviolet photoelectron spectra of gas phase and condensed tin and lead dihalides (MX2 ; M = Sn,Pb; X = Cl,Br, I)

The photoelectron spectra and electronic structures of the methylene dihalides, CH₂X₂ (X = F, Cl, Br and I), have been calculated by the overtapping-spheres SCF-Xα-MS method. The results are in good agreement with experimental data. Calculated assignments of the spectra are also presented and interpreted by assuming interaction between lone-pair and bonding orbitals.     

High-resolution X-ray emission Lα1 and Lβ2 Spectra of Hf, Ta, W, Re, and Os

The shape and relative intensities S _α=I(α_1s )/I(α_1s ), S _β=I(β_1s )/I(β₂) of the short-wavelength X-ray Lα₁ and Lβ₂ satellites arising from the radiative decay of the states corresponding to L ₃ M _4,5 configurations were investigated experimentally for Hf, Ta, W, Re, and Os. It was established that, in the case of W, the values S _α=2.5%, S _β=4.2% are five to seven times larger than those for Hf and Ta, and by (30–60)% smaller than those for Re and Os. On the basis of the obtained values of S _α,S _β, as well as the observed two-component structure of the Lα₁ and Lβ₂ satellites, it is concluded that the Coster-Kronig L ₁-L ₃ M ₅ transitions (CK) are allowed by the energy conservation law even for tungsten, and, starting with this element, they represent a major channel of generation of the states of LL ₃ M ₅ configuration. Possible features of such a process for the W atom are discussed in comparison with those for Re and Os.     

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.