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Kempgens, B.; Köppel, Horst; Kivimäki, A.; Neeb, M.; Cederbaum, Lorenz S.; Bradshaw, A. M.

doi:10.1103/physrevlett.79.3617

Cited by 82 publications

(66 citation statements)

References 26 publications

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“…Moreover, we find that the natural ͑Lorentz-ian͒ linewidth of the bulk component is very narrow, 95Ϯ 3 meV, compared with the surface, 231Ϯ 8 meV ͑the latter is again consistent with SXPS measurements͒. 1,2,8 The value for the Lorentzian linewidth of the bulk C 1s component is similar to that used by Speranza and Minati 4 and that observed in small gas-phase molecules 14 and in diamond; 15 therefore the difference in bulk and surface linewidths may explain the apparent discrepancy between the lifetime broadening measured in SXPS and that which might be expected from comparison with closely related systems. 8,9 The changes in linewidth and asymmetry parameter between bulk and surface are significant and point to notable differences between the response to the core hole at the surface and in the bulk of graphite.…”

supporting

confidence: 88%

Surface and bulk components in angle-resolved core-level photoemission spectroscopy of graphite

Hunt

2008

Phys. Rev. B

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Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Angle-resolved x-ray photoelectron spectroscopy of the C 1s line of highly oriented pyrolytic graphite reveals two components separated by 194Ϯ 6 meV, with markedly different asymmetry parameters and natural linewidth. Analysis of the intensity of these peaks as a function of angle demonstrates that the higher binding-energy peak is associated with the outermost graphite layer͑s͒. The conflicting core-level photoemission data from graphite in the literature are addressed in light of these measurements.

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supporting

confidence: 88%

Surface and bulk components in angle-resolved core-level photoemission spectroscopy of graphite

Hunt

2008

Phys. Rev. B

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“…Neutral-molecule orbital energies were also found to give a reasonable estimate of 2 in the case of ethyne. 23 Calculated values of the 〈ν L ) 0|ν R ) 0〉 overlap integrals in conjunction with eq 1, give splittings of 14 and 11 meV for the V ) 0 states of core-ionized C 2 H 6 and C 2 D 6 , respectively.…”

Section: Discussionmentioning

confidence: 99%

Vibrational Structure and Vibronic Coupling in the Carbon 1s Photoelectron Spectra of Ethane and Deuteroethane

et al. 2001

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The carbon 1s photoelectron spectrum of ethane, C 2 H 6 , has been measured at a photon energy of 329 eV and an instrumental resolution of 70 meV. The spectrum shows a rich vibrational structure which is resolved using least-squares fits to the data. Only C-H stretching and CCH bending modes contribute significantly to the spectrum. The lack of excitation of the C-C stretching mode is explained in terms of changes in hybridization at the spectator carbon. To investigate the possibility of incomplete localization of the core hole, the spectra of C 2 H 6 and C 2 D 6 were measured at higher experimental resolution (35 meV). The spectra are accurately fit by a model based on ab initio calculations of the vibrational energies and the geometry changes following ionization, and including vibronic coupling of the two degenerate, localized hole states. A small splitting on the order of 10-20 meV is found for the 2 A 2u and 2 A 1g core-ionized states.

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“…Figure 3 shows this splitting over a wide range of d, using data points for C 2 H 2 [29], C 2 H 4 [30], as well as our results for 400 and 1000 K. These latter points have been plotted such that the size of their splitting is taken from the experiment while the corresponding value of d is that of the calculation. Clearly, the two points fit very well into the overall picture, confirming our ability to compute d reliably for this system.…”

mentioning

confidence: 99%

Thermal Expansion of Supported and Freestanding Graphene: Lattice Constant versus Interatomic Distance

Pozzo

Alfè

Lacovig³

et al. 2011

Phys. Rev. Lett.

164

159

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By using ab initio molecular dynamics calculations, we show that even where the graphene lattice constant contracts, as previously reported for freestanding graphene below room temperature, the average carbon-carbon distance increases with temperature, in both free and supported graphene. This results in a larger corrugation at higher temperature, which can affect the interaction between graphene and the supporting substrate. For a weakly interacting system as graphene=Irð111Þ, we confirm the results using an experimental approach which gives direct access to interatomic distances. DOI: 10.1103/PhysRevLett.106.135501 PACS numbers: 81.05.ue, 68.65.Àk, 65.80.Ck Graphene's (GR) mechanical [1] and thermal [2,3] properties are crucial for applications such as the cooling of electronic devices [4,5], but their microscopic mechanism is often not well understood [6], in contrast to that of many electronic phenomena [7][8][9][10]. A particular challenge lies in the fact that graphene, while being two dimensional, exists in a three-dimensional world, permitting low-lying vibrational excitations and the formation of large-scale ripples perpendicular to the plane [11,12]. This is also important because it introduces a difference between freestanding GR and the technologically more important supported material.In particular, the thermal expansion coefficient of GR and the underlying microscopic mechanism is currently being debated. For freestanding GR and below % 500-700 K, a state-of-the-art atomistic simulation [13], a nonequilibrium Green's function approach [14], and a harmonic density functional theory (HDFT) calculation [15,16] all show a decreasing in-plane lattice parameter a, i.e., a thermal contraction. Above 900 K or so, the two former techniques show a trend reversal with a thermal expansion, while in HDFT the contraction persists over the entire temperature range studied (up to 2500 K). Experiments clearly confirm the thermal contraction of a below room temperature [3,17], but no high temperature measurements have been reported.In order to clarify this issue and to gain insight into its microscopic origin, we present a study based on ab initio simulations and core level photoelectron spectroscopy. Temperature-dependent ab initio molecular dynamics (AIMD) calculations were performed on both freestanding and supported GR. We have used the VASP code [18] with the projector-augmented wave method [19,20], the Perdew-Burke-Ernzerhof exchange-correlation energy [21], and an efficient extrapolation for the charge density [22]. Single particle orbitals were expanded in plane waves with a cutoff of 400 eV. We used the NPT ensemble (constant particles number N, pressure P, and temperature T), as recently implemented in VASP [23,24]. For the present slab calculations, we only applied the constant pressure algorithm to the two lattice vectors parallel to the surface, leaving the third unchanged during the simulation.In the case of freestanding GR the calculations were done using unit cells of different sizes (8 Â 8, 10 Â...

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Core Level Energy Splitting in the C 1sPhotoelectron Spectrum ofC2H2

Cited by 82 publications

References 26 publications

Surface and bulk components in angle-resolved core-level photoemission spectroscopy of graphite

Surface and bulk components in angle-resolved core-level photoemission spectroscopy of graphite

Vibrational Structure and Vibronic Coupling in the Carbon 1s Photoelectron Spectra of Ethane and Deuteroethane

Thermal Expansion of Supported and Freestanding Graphene: Lattice Constant versus Interatomic Distance

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