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11.
J.P.?GauyacqEmail author A.G.?Borisov A.K.?Kazansky 《Applied Physics A: Materials Science & Processing》2004,78(2):141-147
The local density of states of two model systems formed by an individual adsorbate (Cs or Ar) on a Cu(111) surface is investigated using a wave-packet propagation approach. In both cases a sharp peak appears at the threshold of the 2D Shockley surface-state continuum. This peak is attributed to quasi-stationary states located just below the 2D continuum. Following the existence criterion for a bound state in two dimensions by Simon, such states splitting off the surface-state bottom should appear whenever the surface-state continuum is perturbed by an attractive potential, independently of the existence of atomic-like states bound by the perturbing potential. These findings are discussed in connection with recent observations of peaks located at the surface-state threshold in scanning tunnelling microscopy experiments. PACS 68.37.Ef; 73.20.At; 73.20.Hb; 68.43.-h 相似文献
12.
Background
Growth hormone (GH) plays an incompletely understood role in the development of the central nervous system (CNS). In this study, we use transgenic mice expressing a growth hormone antagonist (GHA) to explore the role of GH in regulating postnatal brain, spinal cord and body growth into adulthood. The GHA transgene encodes a protein that inhibits the binding of GH to its receptor, specifically antagonizing the trophic effects of endogenous GH. 相似文献13.
A novel technique for characterizing thin-film second-order nonlinearities with submicrometer resolution for the film's depth is proposed. This method is substantially a variation of the classic one-beam Maker's fringe technique and uses the second harmonic generated by two noncollinear fundamental beams. Compared with that for the one-beam case, this configuration reduces the coherence length of the process, thus increasing the resolution for the nonlinear depth measurements. The technique has been implemented on thermally poled silica samples, revealing the initial growth of the nonlinear region. 相似文献
14.
A new interferometric multi-photon photoemission scheme has been recently introduced by Güdde et al. [1] and applied to a
study of the n=1 image state on Cu(100). We report on the results of a theoretical modelling of this photoemission scheme
based on a wave function representation. It incorporates both resonant transitions and two-photon non-resonant transitions.
In the case of the n=1 image state on Cu(100), the initial state of the photoemission belongs to a continuum. Summation of
the contributions to the photoemission yield from the various initial states is shown to drastically blur the interference
structure, acting as an efficient dephasing process. The sensitivity of the new scheme and of the one-colour TR-2PPE scheme
to the system dynamical properties is discussed.
PACS 73.20.-r; 78.47.+p; 79.60.-i; 82.53.Kp; 42.50.Md 相似文献
15.
Laia Vilà‐Nadal José Pedro Sarasa Dr. Antonio Rodríguez‐Fortea Dr. Joan Igual Dr. Leonid P. Kazansky Dr. Josep M. Poblet Prof. Dr. 《化学:亚洲杂志》2010,5(1):97-104
DFT calculations were carried out to study 183W NMR chemical shifts in the family of the Keggin anions with formula α‐[XW12O40]q? (X=B, Al, Si, P, Ga, Ge, As, Zn), in the β‐ and γ‐[SiW12O40]4? geometric isomers, in the derivative Dawson anion [P2W18O62]6?, and in the most symmetrical Lindqvist [W6O19]2? anion and its derivative [W10O32]4?. In this article, we show that the geometry employed in the calculation of NMR chemical shifts in polyoxotungstates is extremely important if we want to be quantitative. Using very large basis sets of QZ4P quality and taking into account the conductor‐like screening model (COSMO) to account for solvent effects (aqueous and organic solutions), good geometries were found for the polyoxoanions. From these optimal geometries the 183W NMR chemical shifts were computed with the more standard basis sets of TZP quality and including spin–orbit corrections inside the zero‐order regular approximation (ZORA) to describe the relativistic effects of the internal electrons. With this strategy the mean absolute error between experimental and theoretical values was found to be less than 10 ppm, which is similar to the experimental error. We also discuss how the geometry of the polyoxoanion influences on the shielding. 相似文献
16.
A remarkable effect of circular dichroism, i.e., a difference in photoelectron spectra produced by right and left circularly polarized light in two-color multiphoton ionization of atoms, is predicted for the case when the atom is ionized by an extreme ultraviolet or x-ray femtosecond pulse in the field of a strong infrared laser pulse, both pulses being circularly polarized. We show that the sidebands formed in the spectra exhibit different circular dichroism often of different signs both in angle-resolved and angle-integrated experimental conditions. The effect can be used for detecting and measuring circular polarization of x rays in a spectral range where other methods are not effective. 相似文献
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18.
The results of CNDO/SP calculations do not suppport the current explanation for the strong deviation from axial symmetry of the 13C hyperfine tensor for the CO+ radical on a H—Y type zeolite. 相似文献
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