Surface resonance

Ph. Ebert, B. Engels, P. Richard, K. Schroeder, S. Bluegel, C. Domke, M. Heinrich, K. Urban. Contribution of surface resonances to scanning tunneling microscopy images (110) surfaces of III-V semiconductors. Phys Rev Lett 77 2997, 1996. 

Fig.3. Single particle density of a characteristic surface resonance state on the W((X)1) surface shown in the (110) plane perpendicular to the surface (after Ref. 21).

R. D. Harris, B. J. Luff, J. S. Wilkinson, J. Piehler, A. Brecht, G. Gauglitz, and R. A. Abuknesha, "Integrated Optical Surface Resonance Immunoprobe for Simazine Detection," Biosensors Bioelectronics 14, 3635-3641 (1999). 

Postemak, M., Krakauer, H., Freeman, A. J., and Koelling, D. D. (1980). Self-consistent electronie structure of surfaces Surface states and surface resonances on W(001). Phys. Rev. B 21, 5601-5612. 

See Scanning tunneling spectroscopy Superconductors 332—334 Surface Brillouin zone 92 hexagonal lattice 133 one-dimensional lattice 123, 128 square lattice 129 Surface chemistry 334—338 hydrogen on silicon 336 oxygen on silicon 334 Surface electronic structures 117 Surface energy 96 Surface potential 93 Surface resonance 91 Surface states 91, 98—107 concept 98... 

A. Sternesjo, C. Mellgren and L. Bjorck, Determination of sulphametazine residues in milk by a surface resonance based biosensors assay, Anal. Biochem., 226 (1995) 175-181. 

These wavelength dependent effects are consistent with increased optical coupling to surface resonances with increasing photon energy. Georgiadis and Rich-... 

Similar potential-dependent experiments were performed on Ag(U0) at various visible wavelengths. Unlike the results at 1064 nm (Fig. 5.6b), where the isotropic response is at a minimum at the PZC, a maximum in both the isotropic and anisotropic response is observed near the PZC followed by a rapid decline as the surface is charged positively. Although the analysis is somewhat more complicated for the Ag(110) due to additional parameters in the fit relative to Ag(lll), the results are qualitatively similar to Ag(lll) in that one observes increased coupling to surface resonances with increased photon energy. These resonances are also potential dependent. 

The first surface state was detected as an unexpected bump at — 0.35eV in the energy distribution of the electrons field-emitted by a W(100) tip by Swanson and Crouser in 1966 [35]. Its surface character was claimed on the basis of the sensitivity of the bump to contaminants. It is somewhat ironic that surface resonances in sharp W tips have been recently found to jeopardize local electron spectroscopy of the surface states performed with the STM [36]. 

In many cases there are electronic states with a strong weight in the surface layer, but which are not located in a gap of the projected bulk band structure. The electrons in these states can decay into bulk states much faster than those occupying pure surface states. These states are known as surface resonances. One of these cases occur in the Ru(0001) surface. 

The upper panel of Fig. 10 shows an atomically resolved STM image of a terrace of Ru(0001) including a defect. The lower panel reproduces the STS conductance spectra recorded on clean Ru(0001). It displays a narrow peak located slightly above the Fermi level (110 40meV).a The peak is not detected in spectra recorded above the surface steps, which suggests that it is due to a surface resonance. Total DOS calculations confirm that the peak corresponds to a sharp surface resonance of pz character located on the Ru atoms. The state presents an anisotropic spatial distribution, pointing towards the hep site of the unoccupied layer above the surface, and outwards. 

The collected data on surface excitons and surface phonons are confronted in order to estimate the extent of the weak surface reconstruction of the anthracene crystal. A surface destabilization (relative to the bulk) corresponding to a negative pressure (— 4 kbar) is inferred and thought to lead to angular reconstruction less than or about 10. The observed energy sequence for surface resonances is shown to be compatible only with R 7 van der Waals forces, for both mechanisms proposed. 

Since we treat resonant UV spectroscopy, we summarize this emission in relation to the resonant Raman limit, which we investigate for bulk and surface resonant spectroscopy. 

Here r,(co) shows the effect of the surface reflectivity, which appears as a lorentzian line, centered at the surface resonance, if we neglect the variation of rv(co) with co around the surface resonance ( lOcnU1). The surface excitations are renormalized relative to the bulk-free surface, leading for coupled surface excitons to a frequency shift ds and to a new radiative width rs, both quantities simply related to the complex amplitude of the bulk reflectivity ... 

In the last subsection, we invoked phonons to explain the nonradiative broadening of the surface structures. However, at very low temperature, the surface state at the bottom of the excitonic band cannot undergo broadening either by phonon absorption or by phonon creation the phonon bath at 2 K does not suffice to account for the 3- to 4-cm 1 nonradiative width of the first surface resonance. Nevertheless, we assume the intrinsic nature of this broadening, since it is observed, constant, for all our best crystals.67120... 

LEED 45 Electronic surface resonance band structure of S-covered surface can be described by 2-D free-electron model... 

Andreyev O, Koroteev YM, Snchez Albaneda M et al (2006) Spin-resolved two-photon photoemission study of the surface resonance state on Co/Cu(001). Phys Rev B 74 195416... 

Yu and Halperin (162) observed a -Pt surface resonance from platinum particles initially prepared on silica gel the carrier was removed afterwards with a solution of sodium hydroxide, thus forming a self-supported pow -der sample. Its average particle diameter determined by TEM was 4 nm assuming a log-normal distribution, this corresponds to a dispersion of 0.31. The NMR samples w ere extensively w ashed with, water, dried, and left exposed to the atmosphere. A signal detected at 1.089 G/kHz w as attributed... 

The double-resonance data (Fig. 40a) show that the signal from Pt in the surface of the particles is symmetric around a center position of approximately 1.096 G/kHz. This is an inhomogeneous linewidth there are many different types of surface Pt, each resonating at a slightly different frequency, and the observed signal is an unresolved superposition of all these elementary resonances. In the NMR layer model (Fig. 48), this idea is expanded further it is supposed that the difference in resonance frequency, and therefore also in LDOS, between all elementary surface resonances is less than the difference between typical surface and subsurface resonances. The important distribution of surface LDOS values has its equivalent in the MAS-NMR of adsorbed CO the MAS does not narrow the signal (Figs. 35c and 35d) because its width is due to a distribution of isotropic shifts rather than to shift anisotropies. 

As shown earlier (Fig. 49), the surface resonance of highly dispersed catalysts is broader than that of catalysts of intermediate dispersions, and the fit parameters clearly cannot be transposed between the two groups in very small particles an atom in a given surface site senses the presence... 

A simple test of this suggestion is the comparison of a five-layer slab calculation for the Knight shift in platinum (70) with the spectral fits of the layer model (Fig. 48). In both cases the surface resonance is shifted about 4% to low field wuth respect to the bulk signal, and the subsurface signal is found at approximately the halfway point. Another test is qualitatively to compare experimental results for hydrogen chemisorption on platinum (Fig. 55) with a calculation for hydrogen on palladium (175) in both cases an important diminution of the surface LDOS on the metal is found. 

Only very preliminary values for the surface LDOS are available. They are based on an analysis of the decay of the echo amplitude in terms of a modulation by the /-coupling of Eq. (14). Marginally better fits to the data are obtained by assuming that the value of J for the surface resonance in Pt/carbon-black is larger than that in Pt/oxide (180). If it is confirmed, this result is very remarkable since it implies that the s-like LDOS is higher on the surface than in the interior of the particle. (The value of J is mainly determined by the s-like DOS at E).) In all other platinum catalysts investigated to date, the s-like Ef LDOS is nearly site independent. 

H. Conrad, M.E. Kordesch, R. Scala W. Stenzel (1986). J. Electron Spectrosc., 38,289-298. Surface resonances on Pd(l 11)/H observed with HREELS. 

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