Ultraviolet Photoelectron Spectra Research Articles

Geometry Change on Ionization. Calculation of IV-IA Relaxation Energies for NH3, N2H4 and CH3NH2

Ab initio calculations on the NH3, N2H4 and CH3NH2 molecules and their respective ground- state cations represent the experimentally observed adiabatic and vertical ionization energies with reasonable accuracy. The unusually large IV - IA difference energy for N2H4 is a measure of the considerable change in geometry accompanying ionization. The calculated value of this relaxation energy at the MP3/6-31G** level is 2.3 eV , rather higher than the two experimental measurements of 1.55 eV , based on the band profile of the ultraviolet photoelectron spectrum, and 1.6-1.8 eV , determined from ion-molecule equilibrium measurements. The smaller IV-IA values for NH3 and CH3NH2 are calculated more accurately. Theoretical vibration frequencies are also obtained for the molecular cations.

HeI α photoelectron modulation spectroscopy of H2 and D2

A new method for the determination of photoionization cross sections is presented. The technique is used to obtain cross sections of H2 and D2 relative to those of H and D atoms from accurate HeI α photoelectron intensity measurements. With the virtually exact atomic cross section calculations available for H and D atoms our experiments provide absolute H2 and D2 photoionization cross sections. Ultraviolet photoelectron (UV PE) spectra of vibrationally excited hydrogen (v″=1,2) and deuterium (v″=1,2,3), free from overlapping bands due to vibrational ground state molecules, are presented for the first time. Positions and intensities of all observed features are excellently reproduced using well-known molecular and ionic constants and accurate ab initio potential energy curves. Combination of the cross section determinations of H2 and D2 with intensity measurements of vibrationally excited H2 and D2 reveals some qualitative information on H*2 and D*2 cross sections and β parameters.

Angle-resolved ultraviolet photoelectron spectroscopy of the unoccupied band structure of graphite.

The energy dispersion of conduction (or unoccupied) bands of graphite has been studied by angle-resolved ultraviolet photoelectron spectroscopy. Photoemission peaks originating in the conduction bands were successfully separated from those of the valence bands by comparing two sets of angle-resolved ultraviolet photoelectron spectra excited by the He and He resonance lines. Three conduction bands were found in the energy range of 7--13 eV above the Fermi level and one of them showed a remarkable energy dispersion in the \ensuremath{\Gamma}KHA plane in the Brillouin zone. The present experimental results have been compared with the results of earlier experiments using photoelectron, secondary-electron, electron-energy-loss, photoyield, and inverse photoelectron spectroscopies as well as with some theoretical calculations. The usefulness of angle-resolved (secondary) photoelectron spectroscopy to study unoccupied band structure has been demonstrated.

HeI-Photoelektronen-Spektrum von Cl-NSO

The ultraviolet photoelectron spectrum of the N-chlorothionylimide molecule (Cl-NSO) has been obtained and analyzed. The spectrum is interpreted by comparison with the known spectra of the parent compounds H-NSO, SO2 and the related molecules Cl-NCO and H-NCO as well as with the aid ofab initio SCF-calculations in terms of ionization from the eight highest filled valence molecular orbitals in this molecule.

Ultraviolet photoelectron spectroscopy of oriented carboxylic acid films prepared by vacuum deposition

Ultraviolet photoelectron spectra were measured for films of aliphatic carboxylic acids made by vacuum deposition. Their threshold ionization potentials varied within 0.7 eV according to the measure of molecular orientation. This variation is explained by dimer formation in a highly crystalline film.

Angle-resolved ultraviolet-photoelectron-spectroscopy study of the Si(111) sqrt 3-bar x sqrt 3-bar-Al surface.

Angle-resolved ultraviolet-photoelectron spectra have been measured for the $\mathrm{Si}(111)\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$-Al surface. Two surface-state bands have been found at ${E}_{b}=\ensuremath{\sim}1.3\ensuremath{-}1.9$ eV below the Fermi level which disperse in accordance with the $\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$ surface Brillouin zone. It is suggested that a nondispersive surface-state band found at ${E}_{b}\ensuremath{\approx}0.3$ eV is extrinsic to the $\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$ surface. The two dispersive bands are in qualitative agreement with those calculated for threefold-hollow adatom models.

ChemInform Abstract: A COMPLETE ASSIGNMENT OF THE ULTRAVIOLET PHOTOELECTRON SPECTRUM OF PENTACARBONYL(PENTACARBONYLMANGANESE)RHENIUM

Chemischer InformationsdienstVolume 16, Issue 20 Organoelement Compounds ChemInform Abstract: A COMPLETE ASSIGNMENT OF THE ULTRAVIOLET PHOTOELECTRON SPECTRUM OF PENTACARBONYL(PENTACARBONYLMANGANESE)RHENIUM R. R. ANDREA, R. R. ANDREASearch for more papers by this authorA. TERPSTRA, A. TERPSTRASearch for more papers by this authorD. J. STUFKENS, D. J. STUFKENSSearch for more papers by this authorA. OSKAM, A. OSKAMSearch for more papers by this author R. R. ANDREA, R. R. ANDREASearch for more papers by this authorA. TERPSTRA, A. TERPSTRASearch for more papers by this authorD. J. STUFKENS, D. J. STUFKENSSearch for more papers by this authorA. OSKAM, A. OSKAMSearch for more papers by this author First published: May 21, 1985 https://doi.org/10.1002/chin.198520279Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume16, Issue20May 21, 1985 RelatedInformation

Local-Density Functional Approach to Chain Polymers

Abstract A first-principles, self-consistent computational approach for determining the electronic properties of chain polymers has been developed. The local-density functional formalism in conjunction with a linear combination of atomic orbitals approximation using a Gaussian basis can then be used to calculate band energies and one-electron wave functions for chain polymers. Using perturbation theory, these results can be used to calculate theoretical x-ray and ultraviolet photoelectron spectra. Calculations have been performed for polyacetylene and the heterocyclic ring chain polymers. The resulting photoelectron spectra for polyacetylene are shown to be in excellent agreement with experiment. In addition, a theoretical prediction is made for the photoelectron spectra of polythiophene.

Early stages of epitaxial CoSi 2 formation on Si(111) surface as investigated by ARUPS, XPS, LEED and work function variation

We performed the CoSi 2 formation on a clean (7 × 7) Si(111) surface under UHV conditions. The used techniques were angle resolved UV photoemission, X-ray photoemission, work function change and low energy electron diffraction in order to study the electronic and structural properties of the interface during its formation. At room temperature, a small amount of Co reacts strongly with Si to form an interfacial and very thin cobalt suicide. The ultraviolet photoelectron spectrum displays already two features corresponding respectively to the Co 3d and Si 3p electron bonding states and the Co 3d non-bonding states. With increasing coverage ( θ ≳ 4 ML) it seems that the interfacial suicide prevents further Co−Si interdiffusion to achieve the suicide reaction and a metal rich film is found. At high temperature (∼ 600°C) and in the first monolayer range, several superstructures are found (√7 × √7, and 2 × 2). They are induced by a Co-Si bidimensional compound where the Co atoms are not yet completely surrounded by Si atoms as in their bulk CoSi 2 structure. With increasing coverage, a CoSi 2-like photoemission spectrum is observed reflecting the formation of the disilicide. The LEED pattern testifies an epitaxial growth displaying a (1 × 1) CoSi 2 diagram. The work function change technique also reflects faithfully this growth.

Reinvestigation of the formaldehyde–aniline condensation. Part 4. Ultraviolet photoelectron and electron transmission spectra of N-methyleneaniline and its symmetric dimethyl ring-substituted homologues and semiempirical theoretical evaluations

A study of the vapours over heated 1,3,5-triphenylhexahydrotriazine (III) has been made by u.v. photoelectron and electron transmission spectral techniques. Complementary data are also reported for the homologous derivatives 2,2′,2″,6,6′,6″- and 3,3′,3″,5,5′,5″-hexamethyl-1,3,5-triphenylhexahy-drotriazines. The vapours over these compounds are found to be made up mostly of monomeric N-methyleneaniline (I) and of its dimethyl derivatives, respectively. The ionization and electron affinity data are compared with those of reference molecules. Theoretical MO energies obtained by means of an MNDO program for optimized geometries of (I), its dimer 1,3-diphenyldiazetidine (II), and of the references molecules are compared with the experimental data. It appears that, in the gas phase (ca. 100 °C and 0.0001 Torr)(I) and its dimethyl derivatives adopt a conformation characterized by a strong π(ring)–π(NC) mixing, that is, a nearly coplanar conformation.

A complete assignment of the ultraviolet photoelectron spectrum of MnRe(CO) 10

A complete assignment of the ultraviolet photoelectron spectrum of MnRe(CO) 10

Surface stoichiometry changes induced by the hydrogenation of Hg0.72Cd0.28Te

The reaction of the cleaved Hg0.72Cd0.28Te surface with atomic hyrogen has been studied with ultraviolet photoelectron spectra obtained using synchrotron radiation. Hydrogen exposures of 600 L or less caused no detectable difference in the photoelectron spectra. However, dramatic changes were observed upon extended hydrogenation with the mercury signal decreasing to ∼20% of its original value before the surface passivated at an exposure of l04 L with the apparent formation of hydrogen– Hg and Cd complexes. During hydrogenation, some of the freed Hg diffuses into the semiconductor to form a degenerate n-type surface layer. This process is contrasted to oxidation where no saturation of the surface was seen and the reacted surface was almost completely Hg free.

Intramolecular band mapping of poly(p-phenylene) via UV photoelectron spectroscopy of finite polyphenyls

Abstract Ultraviolet photoelectron spectra were measured of solid sexiphenyl with synchrotron radiation and of gaseous polyphenyls from biphenyl to sexiphenyl with a Hel light source. The similarity of the spectrum of the solid with the XPS spectrum of poly(p-phenylene) (PPP) shows the usefulness of sexiphenyl as a model compound of PPP. Examination of the fine structure observed in the low binding-energy region clearly shows how the electronic structure of the p-phenylenes evolves from that of benzene including the effects of deeper levels and of the non-planarity of the molecular geometry. The experimental E = E(k) energy band-dispersion relation of a PPP chain can be deduced by giving each energy level of the oligomers an appropriate k value. An extrapolation for the total bandwidth and the threshold photoemission energy of solid PPP yields 3.95 and 5.65 eV. respectively.

“Silicide-like electron states in the Si-Mo interface grown at liquid nitrogen temperature”

Ultraviolet photoelectron spectra of the Si(111)-Mo interface grown at ∼ 85° K are presented and compared with spectra of the Mo 4d states at increasing coverages on a substrate of Al. In the sharp transition region between Si and the metal the interface electron states can be understood in terms of the Si(p)-Mo(d) hybridzation; in spite of the sharpness of the interface the electron states in the transition region show the same qualitative features as refractory metal silicides.

A study of the spinel materials LiTi 2O 4 and [formula omitted] by photoelectron spectroscopy

HeI-excited valence-band ultraviolet photoelectron spectra and Mg Kα-excited Ti-2 p X-ray photoelectron spectra are reported for the spinel materials LiTi 2O 4 and Li 4 3 Ti 5 3 O 4 . The presence of a Fermi edge in the ultraviolet photoelectron spectrum of LiTi 2O 4 confirms the metallic nature of this material, although the measured density of states at the Fermi energy is much lower than that expected from an independent-electron interpretation of the magnetic susceptibility. This difference is attributed to a strong interaction of the conduction electrons with the lattice vibrations. The localization of conduction electrons that occurs in the final state in the Ti-2 p X-ray photoelectron spectrum of LiTi 2O 4 is attributed to a Coulomb interaction with a core hole.

Electronic and geometric structure of acetylide carbon on the surface of lithium

The reaction products formed on clean evaporated lithium films exposed to acetylene gas under UHV conditions were examined with ultraviolet photoelectron and Auger electron spectroscopies. Good agreement was obtained between the observed ultraviolet photoelectron spectrum and a spectrum simulated from ab initio calculations for C 2Li 2 in D 2h symmetry. The components of the C(KW) Auger signal were also consistent with carbon being present as C 2 n− units (acetylide) rather than as carbonaceous aggregates or as monomeric carbon. The observed carbon AES structure was fit in good agreement by a simulation using experimental electronic binding energies and Auger transition intensities calculated for C 2Li 2. Saturation of the ultraviolet and Auger electron signals with increasing exposure to HC 2H was not found, although thin films of lithium were slowly consumed on long exposure to acetylene. A loss of the reaction product from the interfacial region was indicated. Cluster models of acetylide on the (100) face of lithium, C 2/Li 8(6, 2)-(100), were used to investigate geometric arrangement of C 2 n− relative to lithium. The results show that acetylide resident in the interface below the first layer of lithiums of the model was energetically favored compared to C 2 n− resident on top of the first layer of lithium. The stability of this conformation was calculated to be further increased by a small expansion of lithiums near neighbor to C 2Li 2. The restructuring calculated for the model complements the absent saturation and suggests that C 2 n− units diffuse into the actual film via a local expansion.

A HAM/3 study of photoelectron spectra of benzoic acid and its derivatives

The ultraviolet photoelectron spectra of benzoic acid and its derivatives in the literature are analysed by the semiempirical HAM/3 method. Agreement between theory and experiment in the low-energy regions of these spectra is satisfactory. HAM/3 assignment is proposed for the high-energy regions of the spectra where no experimental information is available. HAM/3 reproduced very well chemical substitution effects that were observed experimentally.

Ultraviolet photoelectron spectra of gas phase and condensed tin and lead dihalides (MX 2 ; M = Sn, Pb; X = Cl, Br, I)

Etude comparative des spectres de photoelectrons ∂ν des composes, du titre a l'etat gazeux et a l'etat condense

Ultraviolet photoelectron spectra of some resorcinols and dithioresorcinols

The photoelectron spectra of resorcinol, dithioresorcinol, 4,6-dichlororesorcinol 1, 4,6-dichlorodithioresorcinol 3 and their methyl derivatives were recorded by using He(I) and HE(II) excitations. The assignment of the photoelectron bands was mainly based on relative band intensity variations and on the results of ab initio STO-3G calculations. The results show clear evidence of the presence of intramolecular OH … Cl hydrogen bonding interactions in 1, while no effects of such a bonding was observed in the corresponding dithiocompound 3. These findings are confirmed by the STO-3G calculations. The photoelectron spectra of both 1,3-dithiomethoxybenzene and 1,3-dithiomethoxy-4,6-dichlorobenzene give evidence of rotational isomerism of the SCH 3 group.

Vacuum ultraviolet photoelectron spectroscopy of transient species. XVII. The SiH 3(X 2A 1) radical

The first band in the vacuum ultraviolet photoelectron spectrum of the silyl radical, corresponding to the process SiH 3 (X 1A′ 1) ← SiH 3(X 2A 1), has been observed with HeI radiation. Extensive vibrational fine structure associated with the SiH 3 + deformation vibration was observed in this band and analysis of the structure gave a value of ω = 820 = 40 cm -1 for the out-of-plane deformation mode in the ion. The vertical and adiabatic ionization energies were measured as 8.74 = 0.01 eV and 8.14 ± 0.01 eV respectively and use of the latter value together with the established heat of formation of the silyl radical allows an improved heat of formation of SiH 3 -. Δ H 298 0 (SiH 3 -) to be derived as 980 ± 7 kJ mol −1.