Core excitations of naphthalene: Vibrational structure versus chemical shifts

Royal Institute of Technology, S-106 91 Stockholm, Sweden.
The Journal of Chemical Physics (Impact Factor: 2.95). 10/2004; 121(12):5733-9. DOI: 10.1063/1.1784450
Source: PubMed


High-resolution x-ray photoelectron emission (XPS) and near-edge x-ray absorption fine structure (NEXAFS) spectra of naphthalene are analyzed in terms of the initial state chemical shifts and the vibrational fine structure of the excitations. Carbon atoms located at peripheral sites experience only a small chemical shift and exhibit rather similar charge-vibrational coupling, while the atoms in the bridging positions differ substantially. In the XPS spectra, C-H stretching modes provide important contributions to the overall shape of the spectrum. In contrast, the NEXAFS spectrum contains only vibrational progressions from particular C-C stretching modes. The accuracy of ab initio calculations of absolute electronic transition energies is discussed in the context of minute chemical shifts, the vibrational fine structure, and the state multiplicity.

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    • "The XAS results should therefore be considered to be representative for the terrace NDCA adsorbates only. The asymmetric low-energy peak in the X-ray absorption spectrum in Fig. 7 at around 285 eV is attributed to excitations from the naphthalene C 1s levels to the LUMO [27], while the higher energy peak at around 288 eV stems primarily from excitations Figure 7 C 1s X-ray absorption spectra for the same non-annealed submonolayer NDCA/Ag(110) preparation as in Fig. 6(b). An intensity offset was applied to the spectra for reasons of presentation . "
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    ABSTRACT: The adsorption of 2,6-naphthalenedicarboxylic acid (NDCA) molecules on the Ag(110), Cu(110), and Ag(111) surfaces at room temperature has been studied by means of scanning tunnelling microscopy (STM). Further supporting results were obtained using X-ray photoelectron spectroscopy (XPS) and soft X-ray absorption spectroscopy (XAS). On the Ag(110) support, which had an average terrace width of only 15 nm, the NDCA molecules form extended one-dimensional (1-D) assemblies, which are oriented perpendicular to the step edges and have lengths of several hundred nanometres. This shows that the assemblies have a large tolerance to monatomic surface steps on the Ag(110) surface. The observed behaviour is explained in terms of strong intermolecular hydrogen bonding and a strong surface-mediated directionality, assisted by a sufficient degree of molecular backbone flexibility. In contrast, the same kind of step-edge crossing is not observed when the molecules are adsorbed on the isotropic Ag(111) or more reactive Cu(110) surfaces. On Ag(111), similar 1-D assemblies are formed to those on Ag(110), but they are oriented along the step edges. On Cu(110), the carboxylic groups of NDCA are deprotonated and form covalent bonds to the surface, a situation which is also achieved on Ag(110) by annealing to 200 °C. These results show that the formation of particular self-assembled molecular nanostructures depends significantly on a subtle balance between the adsorbate-adsorbate and adsorbate-substrate interactions and that kinetic factors play an important role. KeywordsMolecular self-assembly-hydrogen bonding-scanning tunnelling microscopy-X-ray photoelectron spectroscopy
    Full-text · Article · Jul 2010 · Nano Research
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    • "Besides the peak of adventitious carbon at 284.8 eV, the peak at 286.3 eV is assigned to ether bonding (C ⁎ –O–C) [8], indicating the presence of residue solvent, THF, on the surface of the particles. In addition, a small amount of naphthalene remaining on the surface is verified by the peak at 289.6 eV, which is close to the datum reported previously [9]. The peak at 287.9 eV is ascribed to C ⁎ fO which might derive from absorption of CO 2 in air. "
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    ABSTRACT: In this paper, Mg nanoparticles were prepared in tetrahydrofuran via lithium reduction of the corresponding Mg salt. X-ray diffraction and scanning electron microscope investigations confirm the formation of hexagonal phase Mg particles with an average size of 300 nm. X-ray photoelectron spectrometer analysis indicates that the as-prepared Mg nanoparticles are covered with a protecting layer consisting of residue solvents, naphthalene and Mg(OH) 2 , which slows down further oxidation under ambient conditions. Thermal analysis shows that the rapid oxidation and nitridation processes of the particles take place at around 500 °C and 553 °C, respectively. Furthermore, the addition of a small amount of magnesium nanoparticles remarkably catalyzes the decomposition process of ammonium perchlorate by lowering the decomposition temperature and enhancing its heat output.
    Preview · Article · Apr 2007 · Materials Characterization
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    ABSTRACT: High-resolution C(1s) near-edge X-ray absorption and X-ray photoionization spectra of the free biphenyl molecule are presented and theoretically analyzed in order to allow an assignment of the observed spectral features. Finite lifetime broadening, a high density of vibrational states, and a strong overlap of contributions from chemically different carbon atom sites only partially allow resolving the vibrational fine structure. However, the shape and width of the spectral profiles are strongly determined by both chemical shifts and vibronic effects. In particular, different from photoionization of valence levels, both types of core level spectra do not contain contributions from dihedral modes which are related to the twisting motion of the two phenyl rings. Contrary to naphthalene, C-H stretching modes are significantly enhanced in the core excitation spectra of biphenyl while the contributions from C-C stretching modes are reduced.
    No preview · Article · Mar 2005 · The Journal of Physical Chemistry A
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