Valence photoelectron spectrum of KBr: Effects of electron correlation

The valence photoelectron spectrum has been measured for molecular KBr. Experimental energies of the main and satellite structures have been compared with the results of ab initio calculations based on molecular orbital theory including configuration and multiconfiguration interaction approaches. Comparison between the experimental KBr spectrum and previously reported Kr valence photoelectron spectrum has also been performed in order to find out if electron correlation is of the same importance in the valence ionized state of KBr as in the corresponding state of Kr.     

Valence and C 1s core level photoelectron spectra of camphor

The valence photoelectron spectrum of camphor has been recorded with 95 eV synchrotron radiation, with better definition than previous He I spectra. The spectrum is interpreted by comparison with these He I results and with the aid of an outer-valence Green’s Function calculation of the orbital ionization energies. These calculations closely reproduce the observed vertical ionization energies in the outer valence region. A core level spectrum of the C 1s region (hν=357.9 eV) is also presented and reveals a marked shift of the carbonyl carbon relative to all others in the molecule.     

Valence electron binding energies of some silicon compounds from x-ray photoelectron spectroscopy

X-ray photoelectron spectra in the valence electron region were obtained for gaseous SiH₄, SiH₃CH₃, Si(CH₃)₄, SiH₃Cl, and SiF₄. The experimental ionization potentials and relative peak intensities are consistent with extended Hückel theory MO calculations. The data can be rationalized without assuming substantial participation of silicon d orbitals in the bonding of these compounds.     

Valence band of molybdenum by photoelectron spectroscopy

Experimental photoelectron spectra of a clean polycrystalline Mo surface excited by monochromatized Al K _α X-rays are presented. The spectra are compared with valence bands obtained by UPS and by band structure calculations within the 5 eV region below the Mo Fermi level. All results mentioned above display peaks at 0.3, 1.7, 2.8 and 4 eV belowE _F. The energy distribution of the valence band does not vary with photon energy and electron emission angle for the four different polycrystalline Mo surfaces compared. It is concluded that the four peaks representing the Mo valence band are predominantly of bulk origin.     

Satellite lines in photoelectron spectra

A general theoretical framework is presented for treating satellite line intensities in photoelectron spectra. It is shown that aside from multiplet structure characteristic of open shell systems, satellite lines involve a breakdown of the one-electron or single particle approximation. For any choice of independent electron basis states, this breakdown can be in the form of initial state configuration interaction, final ionic state configuration interaction, or interchannel coupling (configuration interaction) among the various possible photoionization channels (ion plus photoelectron system). This last effect has not been discussed in connection with photoelectron spectroscopy but its consequences can be extremely important.     

The influence of electron scattering on the lineshape of auger and photoelectron spectra

A simplified model of Auger and photoelectron scattering in solids is presented. Within the framework of the model the relation between the distribution of backscattered primary electrons and Auger photoelectron distribution is obtained in terms of the geometric factor and the density of inelastic electron scattering probability. The new algorithm of spectrum background subtraction is formulated and applied to process the X-ray photoelectron and Auger spectra for a series of oxygen, fluorine, and copper compounds. It is shown that the method accuracy for the peak area measurements is better than 10%.     

ESCA applied to liquids. II. Valence and core electron spectra of formamide

A brief review of the technique of applying ESCA to liquid samples is given. A list of solvents suitable for ESCA studies is presented and the particul     

Relative intensities in x-ray photoelectron spectra

An experimental determination of the relative intensities of X-ray photoelectron lines corresponding to the inner levels of elements with Z ? 20, and calculations of the total photo-ionization cross-sections for all shells of these elements with the Hartree—Fock—Slater potential are reported. The experimental and theoretical values agree well for the 1s levels while marked discrepancies are revealed for the 2p levels. The theoretical values of the cross sections for the atomic valence levels are used to calculate the relative intensities of molecular levels in CF₄, BF₄^?, BeF₄^2?, LiF, NO₃^?, CO₃^2?, CO, N₂, CO₂, H₂O and C₄H₅N. The results of the calculations agree satisfactorily with experiment.     

Relative intensities in X-ray photoelectron spectra

An experimental determination of the relative intensities of X-ray photoelectron lines corresponding to the inner levels of elements with Z ? 20, and calculations of the total photo-ionization cross-sections for all shells of these elements with the Hartree—Fock—Slater potential are reported. The experimental and theoretical values agree well for the 1s levels while marked discrepancies are revealed for the 2p levels. The theoretical values of the cross sections for the atomic valence levels are used to calculate the relative intensities of molecular levels in CF₄, BF₄^?, BeF₄^2?, LiF, NO₃^?, CO₃^2?, CO, N₂, CO₂, H₂O and C₄H₅N. The results of the calculations agree satisfactorily with experiment.     

Valence band electron tunneling in metal-oxide-silicon structures

Experimental results are presented for the substrate current appearing in thin oxide metal-oxide-silicon capacitors with a shallow n/p junction beneath the gate when a positive gate voltage in the tunneling regime is applied. The analysis of the current-voltage characteristics shows that for an oxide voltage drop lower than about 5 V the substrate current is due to electron tunneling from the silicon valence band. The dispersion relation in the energy range extending 3 eV below the oxide conduction band is determined from the voltage dependence of the current in the direct tunneling regime. An effective mass of about 0.8m_e is found near the edge of the oxide conduction band, while for lower energies a strong decrease of the effective mass is observed.     

The photoelectron spectra of the halomethanes

The photoelectron bands associated with ionization from the formally non-bonding p orbitals of the halogen atoms in the halomethanes have been interpreted in terms of a pseudo one-electron hamiltonian. Account has been taken of interactions between the halogen atoms, of interactions between the halogen p orbitals and the σ-bonding orbitals, and of spin-orbit coupling. This model leads to a systematic assignment of all the bands of the chloro and bromomethanes, and gives a satisfactory account of the spin-orbit splittings in the bromomethanes.     

X-ray photoelectron spectra of hexavalent iron

Binding energies of Fe 3p and Fe 2p electrons for K₂FeO₄ were measured and compared with those for γ-FeOOH, α-Fe₂O₃, and for metallic iron.     

The photoelectron spectra of the perfluorodiazines

The photoelectron spectra of the three isomeric tetrafluorodiazines have been measured and assigned. Independent support for the assignment is provided by published ESCA data.     

X-ray photoelectron spectra of cobalt compounds

The X-ray photoelectron spectra of a variety of cobalt(II) and cobalt(III) complexes have been investigated. Intense satellite lines were observed for the 2p, 3s and 3p peaks in the case of the high spin cobalt(II) compounds, but not for low spin cobalt(III) complexes. The satellites of the 2p levels are best explained as arising from shake-up processes, whereas those of the 3s and 3p levels are thought to arise largely from multiplet (exchange) splitting of the levels. Multiplet splitting of the 2p level is small and responsible for an increase in the doublet separation of the 2p_1/2, 2p_3/2 spin-orbit levels of the high spin cobalt(II) compounds. The chemical shifts for cobalt differ for the 2p, 3s and 3p levels of the high spin cobalt(II) compounds. Those of the 2p and 3p levels of diamagnetic cobalt(III) and low spin cobalt(II) complexes are equal. The difference in the case of the high spin cobalt(II) compounds is thought to be due to the presence of unpaired 3d electrons.     

UV photoelectron spectra of adsorbed cyclopentadienyl

Angle resolved photoelectron spectra stimulated by synchrotron radiation are reported for cyclopentadienyl (Cp) adsorbed on Rh(III). Molecular orbital assignment of Cp derived photoemission bands is attempted by comparison with gas phase monometal-Cp complexes, MO calculations and by considering polarisation dependence and angular variation in the present oriented-molecule spectra. The spectra are discussed in terms of the intramolecular symmetry and of the symmetry of the total adsorption complex.