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.     

Shifts of electronicKX-rays in muonic atoms

Energies of electronicKX-rays in muonic atoms were calculated for muons in various outer orbitals and for different numbers of electrons. Energy shifts were obtained with respect to characteristic X-rays belonging to nuclear charge (Z?1) and their possible observation is discussed. The shifts in muonic Sn as an example amount to 19, 37, and 59 eV for the muon in 5g, 6h, and 7i states respectively. However, shifts due to the number of electrons present and the electron vacancy distribution in theL-shell are significantly larger. Accurate measurements of theKX-ray energies would therefore enable us to learn more about the electronic structure during the muonic cascade.     

Electrons ejected in resonant Raman scattering of X-rays on krypton

In the resonant Raman scattering of x-rays on krypton gas the ejected electrons were investigated by a proportional counter spectrometer. The cross sections for the process were determined for three energies of the incident photons (181 eV, 89 eV, and 33 eV below theK edge). The results agree with the theoretical predictions, thus independently confirming the theory that has so far only been tested by scattered photon data. From the cross sections the width of theK-shell excited state of krypton is extracted asΓ _K =(2.75±0.10) eV.     

Chemical shift analysis of S(Kβ) X-ray emission in As,S alloys

Some aspects of chemical bonding in amorphous arsenic-sulphur alloys have been investigated by observing the sulphur K_β X-ray flouorescence line excited by high energy electrons. The splitting of the S(K_β) peak as well as the relative intensity variation with As, S composition is interpreted in terms of a chemical shift of the sulphur energy levels. Estimates of the effect of the incorporation of arsenic on the atomic energy levels in sulphur are consistent with the observed values of the S(K_β) X-ray emission energy.     

Laser-induced nonthermal fragmentation of C60 studied by semiclassical dynamics simulation

Photofragmentation of the C₆₀ fullerene induced by ultrafast laser pulses is studied by semiclassical dynamics simulation. The simulation study is focused on the excitation below the continuum levels. A laser pulse of 40 fs (FWHM) with an effective photon energy of 2.0 eV and different intensities was selected to interact with the C₆₀ fullerene. The simulation results show that averaged fragmentation size distribution over groups of initial geometries selected at random exhibits a power law pattern with the peak at C₂ at high laser pulse intensities. The threshold for the C₆₀ fragmentation was determined. The simulation finds that as many as 55 electrons are excited from the occupied molecular orbitals to unoccupied molecular orbitals upon the laser irradiation and that the number of the fragments significantly depends on the number of electrons excited. Finally, the temperature examination seems to suggest that the nonthermal effect may play a significant role in laser fragmentation of the C₆₀ fullerene.     

Theoretical study of low lying electronic states of GdO

Low lying electronic states of GdO have been investigated by complete active space SCF (CASSCF) and multireference singly and doubly excited configuration interaction (MRSDCI) calculations using the model core potential (MCP) method. The 4f electrons of Gd were included explicitly in the valence space. Relativistic effects were incorporated in the MCP and basis sets for Gd at the level of Cowan and Griffin's quasirelativistic Hartree—Fock method. The ⁹Σ^? state (f⁷σ) was the ground state, and excited states, ⁹Δ, ⁹Π, 2⁹Σ^?, ⁷Σ^?, ⁷Δ, ⁷Π, and 2⁷E^?, lay between 0 ～ 22 300 cm^?1. The energy separations for these states agreed well with available experimental values. Calculated GdO bond lengths and vibrational frequencies for these states are in the ranges of 1.81–1.85 Å and of 800–880 cm^?1, respectively. Mulliken population analysis showed that the gross population of the 4f orbitals was 7.1 e for all these states, and that the 4f electrons were strongly localized on Gd atom. The effective charge distribution was approximated to be Gd⁺O^?. The σ and π bonding orbitals were mainly formed by Gd 5d and O 2p orbitals.     

The decay of174Ta

Levels in¹⁷⁴Hf excited in the decay of¹⁷⁴Ta have been studied. Measurements of gamma-rays, conversion electrons and gamma-gamma-time coincidences were performed. The ground state band, the beta-vibrational band, the gamma-vibrational band with its head at 1226.81 keV, aK=3⁺ band at 1303.42 keV and aK=2^? octupole band at 1308.67 keV were observed. Several 2⁺ levels withK=0 are excited. The mainβ ⁺-branches proceed through allowed or first-forbidden transitions to the 2⁺ and 4⁺ levels of the ground state band. The character of theI ^π=3⁽⁺⁾ ground state of¹⁷⁴Ta is discussed.     

Generalization of the variational principle and the Hohenberg and Kohn theorems for excited states of Fermion systems

Through the entanglement of a collection of K non-interacting replicas of a system of N interacting Fermions, and making use of the properties of reduced density matrices the variational principle and the theorems of Hohenberg and Kohn are generalized to excited states. The generalization of the variational principle makes use of the natural orbitals of an N-particle density matrix describing the state of lowest energy of the entangled state. The extension of the theorems of Hohenberg and Kohn is based on the ground-state formulation of density functional theory but with a new interpretation of the concept of a ground state: It is the state of lowest energy of a system of KN Fermions that is described in terms of the excited states of the N-particle interacting system. This straightforward implementation of the line of reasoning of ground-state density functional theory to a new domain leads to a unique and logically valid extension of the theory to excited states that allows the systematic treatment of all states in the spectrum of the Hamiltonian of an interacting system.     

The determination of theK-shell fluorescence yield of xenon by use of the proportional counter method

The wall-less proportional counter filled with propane with a small admixture of xenon was used as a spectrometer of electrons emitted by xenon atoms when photoelectrically excited by americium-241γ-rays and erbiumKα rays. TheK-shell fluorescence yield of xenon as extracted from spectra ammounts toω _k=0.889(1±0.01).     

Atomic orbitals and photoelectron intensity angular distribution patterns of MoS2 valence band

The ratio of atomic orbitals contributing to the valence band can be determined from the photoelectron intensity angular distribution (PIAD) by using linearly polarized light and display-type spherical mirror analyzer. The experiment was done for MoS₂ using a linearly polarized light at the photon energy of 45 eV perpendicularly incident to the sample surface. Atomic orbitals contributing to the bands near the Fermi level were investigated. The PIAD patterns around the Γ point showed splitting of intensity. The intensity at the top and bottom K points was strong, while the intensity was weak at the left and right side K points. The PIAD patterns from various kinds of atomic orbitals were calculated. By comparing the experimental PIAD patterns to the simulated ones, we concluded that at the Γ point Mo 4d_z2 and S 3p_z atomic orbitals are the main components and at the K points the Mo 4d_xy atomic orbital is dominant. The atomic orbital Mo 4d_x2−y2 also gives contribution to the PIAD pattern. These results were in good agreement with the coefficients of the atomic orbitals derived using ab initio band calculation.     

Charge-state distributions and the population of x-ray emitting states

The population of excited states of neon projectiles has been deduced from highresolution x-ray spectra. From the comparison of the satellite and the hypersatellite spectrum we conclude that the population of the outer shells is insensitive to the presence of either one or twoK-shell vacancies. On the basis of a model of independent electrons the population distribution including states with filledK-shell can be estimated. The deduced mean charge states compare rather well with results obtained from beam analysis over a projectile energy range from 5 to 18 MeV.     

Experimental evidence for strong plasmon coupling in the soft X-ray appearance potential spectrum of graphite

Plasmon satellite structure is known to be weak in X-ray absorption experiments because of the effective cancellation between the couplings to the conduction electrons of the excited electron and core hole. Data on the soft X-ray appearance potential spectrum for the K-shell excitation of graphite however are shown to exhibit strong plasmon effects illustrating the enhanced coupling that results from the creation of an additional conduction electron.     

Spin-polarized relativistic calculations on highly ionized molybdenum

The energies of K_α X-ray satellite lines of molybdenum ionized to different degrees in the L shell with closed and open outer shells (n=3,4 and 5) are reported in this work. The calculations have been carried out using Xα method with spin-polarized single configuration relativistic Dirac-Fock wavefunctions. Calculations have also been carried out with un-polarized relativistic wavefunctions. The effect of relativistic spin exchange potential on the total energies of the various states ionized to different degrees in the inner and outer shells are analyzed. As the transition assignments in the spin-polarized treatment of atomic orbitals take into account the spin orientations of the electrons in the initial and final states, the present calculations elucidate the significance of this technique in giving unique spin-dependent transition assignments to experimental energies.     

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.     

Molecular orbital analysis of the CO32− ion by studies of the anisotropic X-ray emission of its components

The K X-ray emission spectra of carbon and oxygen in calcite single crystals CaCO₃ were measured. Owing to the polarization of the radiation the shape of both spectra shows a pronounced angular dependence, which makes it possible to separate the contributions of the π- and σ-valence electrons of the CO₃^2? ion to the X-ray spectra, and to determine the sequence and the binding energies of the valence orbitals.     

Nonlinear optical spectroscopy of (La0.6Pr0.4)0.7Ca0.3MnO3 manganite

The electronic structure of doped orthorhombic (La_0.6Pr_0.4)_0.7Ca_0.3MnO₃ manganite is studied using the second optical harmonic generation method. The analysis of the frequency and polarization dependence of the intensity related to the second harmonic demonstrates that the applied magnetic field stimulates a transition of spin-polarized electrons from the d orbitals of Mn ions to the p orbitals of O₂ ligands. The manifestation of such transition in the orthorhombic RMnO₃ manganite with the distorted crystal lattice is attributed to the dipole-forbidden electronic transitions arising in the applied magnetic field. The mechanism of magnetooptical activity induced by the charge transfer between Mn and O ions is discussed.     

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.     

Photoelectron spectra of bis-cyclopentadienyl metal dihalides

He(I) and HE(II) photoelectron spectra are reported for (η-C₅H₅)₂MX₂ (M = Ti; X = F, Cl, Br, I: M = Zr, Hf; X = Cl, Br: M = Ta; X = Cl, Br) and (η-MeC₅H₄)₂MX₂ (M = Nb, X = Cl: M = Mo; X = Cl, Br, I). A substantial variation is found in the ordering of the halogen and cyclopentadienyl ionizations, the order being dependent on the metal as well as on the halogen. The compounds may be divided into three classes, namely, those in which the electrons in cyclopentadienyl e₁ orbitals ionize at a lower energy than those occupying halogen pπ orbitals, those in which halogen pπ electrons have lower ionization energy than cyclopentadienyl e₁ electrons and those in which the corresponding electrons arise from extensively delocalized molecular orbitals with significant contributions from both these categories of fragment orbital.     

Photoelectron spectroscopy of molecular systems and quantum-chemical calculations in terms of the density functional theory: Iron π complexes L-Fe(CO)3

The HeI and NeI photoelectron spectra of irontricarboniyl complexes with cyclic diene ligands—αmethylstyrene, orthoquinodimethane, and cyclooctatetraene—were obtained. The results of quantum-chemical calculations of the molecules of these compounds in the approximation of the density functional theory (B3LYP/6-31G*) are presented. It is shown that this approximation describes well the excited ionic states of the π complexes under study. The relative ionization cross sections σ_π and σ_3d , which characterize the probability of removal of electrons from the molecular π-ligand and 3d-metal orbitals, are estimated. The mechanism of the selective coordination of the Fe(CO)₃ groups to corresponding organic ligands is discussed. The energies of the L-Fe(CO)₃ chemical bond are calculated.