Showing papers on "Photoemission spectroscopy published in 1974"
TL;DR: In this article, the relationship between the observed behavior of photoemission energy distributions vs frequency, angle, etc., and the quantum theory of photo-emission as recently set forth formally by Caroli et al. is described.
Abstract: We describe the relation between the observed behavior of photoemission energy distributions vs frequency, angle, etc., and the quantum theory of photoemission as recently set forth formally by Caroli et al. We derive a Fermi's Golden-Rule formula for the angle- and energy-resolved photocurrent from an independent electron solid, and show in detail the approximations which render this formula equivalent to that of the familiar three-step model of bulk photoemission. In terms of the Golden-Rule formula, we account for the direct-transition band-structure regime generally observed at low photon energies (hν≲20−30 eV) and the "photoemission density of states", or x-ray-photoemission-spectroscopy regime, observed at higher energies. We also propose an explanation of Feuerbacher et al.'s observation of "direct photoemission into the vacuum" from single-crystal tungsten surfaces. Finally, we discuss the criteria which determine the relative magnitudes of photocurrents from a surface adsorbate layer and an underlying substrate.
364 citations
TL;DR: In this paper, the adsorption of atomic hydrogen on silicon (2 × 1 cleaved, (111) 7 × 7, and (100) 2 × 1 surfaces has been studied by using electron energy loss spectrscopy (ELS) and photoemission spectroscopy (UPS).
189 citations
TL;DR: In this paper, the authors compared X-ray photoemission spectroscopy (XPS) data for the valence bands of Rh, Pd, Ag, Ir, Pt, and Au with densities of states calculated from interpolated band structures.
Abstract: X-ray photoemission spectroscopy (XPS) data for the valence bands of Rh, Pd, Ag, Ir, Pt, and Au are compared with densities of states calculated from interpolated band structures. The parameters of the interpolation scheme were obtained in an earlier paper by fitting first-principles augmented-plane-wave calculations, and then making adjustments, where necessary, to the width of the $d$ bands in order to improve agreement with ultraviolet photoemission spectroscopy (UPS) data. In the $4d$ metals, Rh, Pd, and Ag, there is excellent agreement between the energy positions of peaks in the occupied density of states and the XPS valence bands. In the $5d$ metals, Ir, Pt, and Au, the agreement is reasonable, but inferior to that for the $4d$ metals particularly in the middle of the $d$-band region. It is argued that the main discrepancies in peak locations are not significant and are most likely due to the approximations in the interpolated band structures, particularly those involved in the spin-orbit splitting and hybridization. The relative intensity of the XPS data in the lower-energy region of the $d$ bands is consistently lower than that in the density of states, indicating appreciable modulation of the spectra by optical-transition strengths.
144 citations
IBM1
TL;DR: In this paper, a comparison of ultraviolet-photo-emission, valence-orbital spectra (as well as high-resolution, x-ray photoemission and N-core-level spectra) of TTF-TCNQ, neutral TCNQ and TTF+TCNQL indicates a large amount of charge transfer.
Abstract: Comparison of ultraviolet-photoemission, valence-orbital spectra (as well as high-resolution, x-ray photoemission, N-core-level spectra) of TTF-TCNQ, neutral TCNQ, and ${\mathrm{K}}^{+}$ ${(\mathrm{TCNQ})}^{\ensuremath{-}}$ indicates a large amount of charge transfer in TTF-TCNQ. The spectra for this complex show strong coupling between states near the Fermi energy and molecular vibrations due to localization of the mobile electrons on individual molecules, at least on the time scale of bond vibrations.
118 citations
TL;DR: In this paper, the third-order Rayleigh-Schrodinger perturbation theory is used to evaluate vertical ionization potentials of closed-shell molecules, and the method is tested with double-zeta calculations on H2O, CH2, NH3, H2CO and F2O.
Abstract: Ordinary third‐order Rayleigh‐Schrodinger perturbation theory is used to evaluate vertical ionization potentials of closed‐shell molecules. The method is tested with double‐zeta calculations on H2O, CH2, NH3, H2CO, and F2O. The results are compared with the ΔSCF method and discussed. On the basis of our calculations, we confirm the suggested alternative assignment for the photoelectron spectrum of F2O, instead of the original assignment based on Koopmans' theorem.
112 citations
TL;DR: In this article, the authors used photoemission spectra obtained from synchrotron radiation from an electron storage ring, a double-pass, electrostatic, electron energy analyzer, and samples cleaved and measured in situ in ultrahigh vacuum.
Abstract: We determine bandwidths and critical-point positions with respect to the valence-band edge for the valence bands of several extensively studied semiconductors (with an accuracy of about 0.3 eV) by using photoemission densities of states derived from photoemission spectra obtained in the 24-78-eV photon energy range. These photoemission spectra were obtained using synchrotron radiation from an electron storage ring; a double-pass, electrostatic, electron energy analyzer; and samples cleaved and measured in situ in ultrahigh vacuum. We give a detailed description of the data-reduction techniques by which electronic state densities and certain valence-band feature positions are determined from photoemission spectra. This description includes a discussion of the effect of various phenomena such as optical-transition-probability variations and Auger-emission peaks. Tables are presented which compare our valence-band-position values with the results of both empirical calculations fit to optical data as well as ab initio calculations. We find systematic and significant differences between experiment and calculations fit only to optical data, these differences increasing with crystal ionicity, while ab initio calculations generally give a better fit to experiment.
106 citations
TL;DR: In this paper, CNDO calculations for CO chemisorbed on a cluster of 10 Ni atoms produce a pattern of valence orbital energy levels that agree well with the experimental photoelectron spectrum of CO adaption on Ni; thus allowing the experimental energies to be assigned to specific orbitals.
Abstract: CNDO calculations for CO chemisorbed on a cluster of 10 Ni atoms produce a pattern of valence orbital energy levels that agrees well with the experimental photoelectron spectrum of CO adsorbed on Ni; thus allowing the experimental energies to be assigned to specific orbitals. The bonding of the carbon atom to the Ni atom largely involves nickel s and p orbitals, with little contribution from the d orbitals.
102 citations
TL;DR: The first X-ray photoemission spectroscopy (XPS) experiments performed at Stanford Synchrotron Radiation Project (SPEAR) were reported in this paper, where the authors reported the first XPS experiments at Stanford Positron Electron Accelerator Accelerator Ring.
Abstract: WE wish to report the first X-ray photoemission spectroscopy (XPS) experiments performed at Stanford Synchrotron Radiation Project, using synchrotron radiation from the Stanford Positron Electron Accelerator Ring (SPEAR) facility. The photoemission technique has been used extensively in the study of the electron properties of materials1,2.
97 citations
TL;DR: In this article, He I and He II spectra for the isoelectronic molecules CF2 and O3 were reported with the aid of semi-empirical molecular orbital calculations.
Abstract: He I and He II spectra are reported for the isoelectronic molecules CF2 and O3. New values are reported for the first and higher ionization potentials. The spectra are interpreted with the aid of semi-empirical molecular orbital calculations.
82 citations
TL;DR: In this article, the authors describe adsorption studies of serveral inorganic and organic species on single crystal Ni(111) using ultraviolet photoemission spectroscopy (hv=21.2 eV).
Abstract: We describe adsorption studies of serveral inorganic and organic species on single crystal Ni(111) using ultraviolet photoemission spectroscopy (hv=21.2 eV). Adsorbate orbital ionization energies and line shapes have been measured and surface reactions have been studied. Ionization energies for chemisorbed unsaturated hydrocarbons (C2H2, C2H4, and C6H6) exhibit large surface-induced relaxation shifts (~1–3 eV) relative to their gas phase counterparts as well as π-orbital bonding shifts (~0.9–1.5 eV). We estimate these π-d bonding interaction strengths and chemisorption energies using Mulliken's donor-acceptor theory as described by Grimley for weak chemical bonds and show that an observed surface reaction, i.e. the dehydrogenation of chemisorbed ethylene (C2H4) to chemisorbed acetylene (C2H2) for T\gtrsim230 K, becomes exothermic only for the chemisorbed species due to the π-d electron interaction.
68 citations
TL;DR: The high resolution 584 A photoelectron spectrum of ozone has been recorded in this paper, where the vertical IP's are found at 12.75 Ev (2A1), 13.03 eV 2A2, 13.57 eV (2B2) and 20.3 eV 3.
TL;DR: In this paper, the four main bands of the spectra of butatriene (I), tetradeuterobutatriene(II), tetramethylbutatriene, III and tetra-t -butyl-butylbutyl butatrienes (IV) are reported and discussed.
TL;DR: In this article, a consistent energy level model of both filled and empty states was constructed from the ultraviolet photoemission spectroscopy (UPS) and electron ELS data, using thermally grown films prepared in ultrahigh vacuum (p ∼ 10−10 Torr).
Abstract: The electronic structure of GeO2 and SiO2 has been studied by ultraviolet photoemission spectroscopy (UPS) and electron energy loss spectroscopy (ELS) using thermally grown films prepared in ultrahigh vacuum (p ∼ 10−10 Torr). A consistent energy level model of both filled and empty states is constructed from the UPS and ELS data. The filled states correspond to localized bonding or nonbonding O(2p) molecular orbitals. The empty states observed in ELS correspond to excitons formed from either localized antibonding states or more extended ``conduction'' band states.
TL;DR: In this paper, the vacuum ultra-violet photoelectron spectrum of sulphur monoxide (SO) has been obtained using a He I 58.4 mm light source and six ionisation potentials (i.p.) of SO(3Σ-) have been determined.
Abstract: Sulphur monoxide (SO) has been produced in the gaseous phase by electrodeless discharge of sulphur dioxide + rare gas mixtures and by the reactions of atomic oxygen with carbon disulphide or hydrogen sulphide. The vacuum ultra-violet photoelectron spectrum of SO has been obtained using a He I 58.4 mm light source.Six ionisation potentials (i.p.) of SO(3Σ–) have been determined. The values for the adiabatic i.p. values are 10.31, 13.50, ∼14.4, 14.94, 16.44 and ∼19.6 eV. CNDO calculations, including the effects of configuration interaction, have been made in order to identify the ionic states which have been formed. Four of the five bands show well-resolved vibrational fine structure which has been analysed in order to assist with identification of the ionic state formed. The first band also shows structure due to spin-orbit coupling. The relative intensities of the vibrational fine structures within a band have been compared with calculated Franck–Condon factors in order to estimate the bond lengths of the ion in its various states. These bond lengths and the measured vibrational level separations have been used with the known i.p. values of atomic sulphur and oxygen to construct a potential energy diagram for SO+.
TL;DR: In this article, the decay of K + 3 p -core excitons in KI was studied by using new methods for obtaining photoemission spectroscopy data with synchrotron radiation.
Book•
01 Jan 1974
TL;DR: In this paper, photoelectron spectra for the tetroxides, RuO4 and OsO4 were obtained in the gas phase with He-I radiation and the nature of the metal-oxygen bonding in these molecules, as inferred from the spectrometric data, was discussed.
Abstract: Photoelectron spectra excited in the gas phase with He-I radiation are reported for the tetroxides, RuO4 and OsO4, and for the oxychloride species VOCl3, CrO2Cl2 and MoO2Cl2. The X-ray photoelectron spectrum of OsO4 has also been measured. The nature of the metal-oxygen bonding in these molecules, as inferred from the spectrometric data, is discussed.
TL;DR: The He 1 photoelectron spectrum of hydrogen peroxide is reported in this paper, showing a splitting of 1.0 eV between the first two bands due to the oxygen nonbonding orbitals.
TL;DR: In this article, X-ray photoelectron spectra in the valence electron region were obtained for gaseous SiH 4, SiH 3 CH 3, Si(CH 3 ) 4, SiH3 Cl, and SiF 4, and the experimental ionization potentials and relative peak intensities are consistent with extended Huckel theory MO calculations.
TL;DR: In this paper, the factors which determine the resolution and sensitivity of electron spectrometers are discussed, mainly from an electron-optical point of view, and three different schemes for monochromatizing the exciting X-radiation are compared.
Abstract: The factors which determine the resolution and sensitivity of electron spectrometers are discussed. Various types of instruments commonly used in X-ray or ultraviolet photoelectron spectroscopy are reviewed, mainly from an electron-optical point of view. The influence of fringing fields and preretardation on resolution and sensitivity is considered. Three different schemes for monochromatizing the exciting X-radiation are compared.
TL;DR: The He II photoelectron spectrum of N2 between 23.5 and 28.0 eV taken at high resolution makes it possible to propose an extension of the known region of the C2Σu+ state as mentioned in this paper.
Abstract: The He II photoelectron spectrum of N2 between 23.5 and 28.0 eV taken at high resolution makes it possible to propose an extension of the known region of the C2Σu+ state of N2+. Comparison is made with band-spectroscopic data and recent mass-spectrometric data.
TL;DR: In this paper, a phase-sensitive detection technique, which enhances the relative signals from transient species present in a discharge system, is described and discussed, and two additional new states of O+2 which are present in the O2(1Δg) spectrum compared with O 2(3Σ-g) are identified as 2 Δg and 2 Δu with the aid of restricted open shell INDO-SCF calculations including the effect of configuration interaction.
Abstract: The vacuum ultra-violet photoelectron spectrum of O2(3Σ–g) and O2(1Δg) obtained using He I radiation, is presented. A phase-sensitive detection technique, which enhances the relative signals from transient species present in a discharge system, is described and discussed. The two additional new states of O+2 which are present in the O2(1Δg) spectrum compared with O2(3Σ–g) are identified as 2Δg and 2Φu with the aid of restricted open shell INDO-SCF calculations including the effect of configuration interaction. The energies of the 2Φu and 2Δg states are ∼6.59 and 7.72 eV respectively above that of the X2Πg ionic state. The bond lengths of these two states and of the 2Σ–g state have been obtained by comparison of observed band intensities with those determined by a Franck–Condon calculation, using a procedure which is described. These bond lengths are ∼1.40, 1.33 and 1.30 A for the 2Φu, 2Δg and 2Σ–g states respectively. The He II spectrum showed a further new state of O+2 which is tentatively identified as 2Δu. Higher states of O+2 which have been observed in ESCA studies are also assigned.
TL;DR: In this paper, the photoelectron spectrum of naphthacene polycrystal was obtained with a high-resolution photo-electron spectrometer using a helium 21.22 eV light source, and the vibrational fine structures were examined.
Abstract: The photoelectron spectrum of naphthacene polycrystal was obtained with a high-resolution photoelectron spectrometer using a helium 21.22 eV light source, and the vibrational fine structures were examined. The resolution, 21 meV FWHM for the argon P3⁄2 peak, became much better than that obtained by means of a retardingpotential-type electron analyzer. Broad peaks with no distinct intramolecular vibrational structure were observed, and the origin of the peak width was discussed.
TL;DR: In this paper, the adsorption of a series of gases onto clean evaporated films of polycrystalline nickel has been studied using ultraviolet and X-ray photoelectron spectroscopy.
Abstract: The adsorption of a series of gases onto clean evaporated films of polycrystalline nickel has been studied using ultraviolet and X-ray photoelectron (u.p.e. and X.p.e. respectively) spectroscopy. Observation of the intensity of photoemission from states close to the Fermi level enables conclusions to be drawn regarding the nature of the adsorbate–metal bond. Different mechanisms are shown to be involved between the two series CO—, C2H4—, O2— and H2S—Ni, and H2O—, CO2—Ni. It is further demonstrated that u.p.e. may be used to follow a surface reaction; results show the progressive displacement by O2 of CO adsorbed on clean Ni. Interpretation of the ultra-violet spectra of adsorbed species is discussed in terms of a possible correlation with energy states of the free molecules.
TL;DR: In this article, the electronic structure of TTF has been determined from its photoelectron spectrum and the photo-electron data for the tetrahydro derivative TTF and 1,3-dithiolane.
Abstract: The electronic structure of tetrathiofulvalene (TTF) has been determined from its photoelectron spectrum and the photoelectron data for the tetrahydro derivative of TTF and 1,3-dithiolane. Correlat...