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Träfflista för sökning "WFRF:(Brito R.) srt2:(2000-2004)"

Sökning: WFRF:(Brito R.) > (2000-2004)

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  • Feifel, R., et al. (författare)
  • "Hidden" vibrations in CO : Reinvestigation of resonant Auger decay for the C 1s → π* excitation
  • 2002
  • Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 1050-2947. ; 65:5 A, s. 527011-527018
  • Tidskriftsartikel (refereegranskat)abstract
    • The higher vibrational levels of the C 1s→π* excitation in carbon monooxide (CO) were investigated by using resonant Auger electron spectroscopy. The absorption profile of the CO was recorded in the partial electron yield mode. The results showed that the vibrational states were not seen in a total yield absorption spectrum whereas they were shown to be discernable in a partial electron yield spectrum.
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  • Marinho, R. R.T., et al. (författare)
  • Interference between direct and resonant channels in near-resonance photoemission in argon
  • 2001
  • Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947. ; 63:3, s. 325141-325145
  • Tidskriftsartikel (refereegranskat)abstract
    • The photoelectron spectra of argon was demonstrated during resonant photoemissions. The interference effects of the photoelectron spectra of argon was monitored by following the intensity of final states through resonant and direct channels. The need for a unified one-description of the ionization through a direct and core-excitation mediated channel was described.
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6.
  • Tchaplyguine, Maxim, et al. (författare)
  • The size of neutral free clusters as manifested in the relative bulk-to-surface intensity in core level photoelectron spectroscopy
  • 2004
  • Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 120:1, s. 345-356
  • Tidskriftsartikel (refereegranskat)abstract
    • A new approach for obtaining an estimate of the effective size of the free neutral clusters is proposed. The approach relies on an experimental measure of the surface and interior or "bulk" cluster atoms provided by the x-ray photoelectron spectroscopy and on a model for the attenuation of photoelectrons ejected from the bulk of the cluster as the result of the ionizing irradiation. The experimental part gives the ratio of the electron signal from the bulk cluster atoms to that from the cluster surface atoms for a wide range of cluster sizes and electron kinetic energies. The attenuated response of the bulk atoms is modeled using an exponential law with the cluster size and kinetic-energy-dependent electron escape depth as parameters. For the experimental size range, model-based calculations for Ar, Kr, and Xe clusters are presented. The cluster size estimates obtained from comparison of the model calculations and experimental results agree well with those determined from the parameters of the cluster creation process. The combination of experiment and modeling also makes it possible to estimate the effective escape depth for electron propagation in free clusters. For Ar, Kr, and Xe clusters of varying mean size, absolute determination of the surface and bulk electron binding energies of the core levels used in the experiments has also been made. (C) 2004 American Institute of Physics.
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  • Baev, A., et al. (författare)
  • Geometrical information on core-excited states obtained from interference quenching of vibrational states in resonant x-ray photoemission
  • 2003
  • Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 67:2
  • Tidskriftsartikel (refereegranskat)abstract
    • An interference quenching of the m=1 final state vibrational line in the resonant Auger decay of N 1s-->pi(*) core-excited N-2 is observed and analyzed. The intensity ratio between the m=1 and m=0 vibrational levels of the X (2)Sigma(g)(+) final state shows a surprising nonmonotonic variation as a function of frequency detuning, going through a minimum with a complete suppression of m=1. We have developed a simple model which indicates a linear relation between the value of the detuning frequency for this minimum and the equilibrium bond distance of the core-excited state. This implies the possibility of determining the equilibrium bond distances for core-excited states to a high degree of accuracy. Simultaneously with the simple model we present a strict theory of the studied effect. This strict theory allows us to explore the accuracy of determining the bond length of the core-excited state from resonant Auger spectra. We obtain a weak influence of the core-hole lifetime on the determined bond length, whereas the number of intermediate vibrational states accounted for in the numerical simulations seems to be quite important.
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9.
  • Bueno, AM, et al. (författare)
  • Influence of chemical bonds on the lifetime of the molecular-field-split 2p levels in H2S
  • 2003
  • Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 67, s. 22714:1-7
  • Tidskriftsartikel (refereegranskat)abstract
    • Different lifetime broadenings in molecular-field-split 2p core levels in H2S are predicted theoretically and are identified in an experimental investigation of the S 2p Auger electron spectrum. The measurements were performed for the transition to the vibrationally resolved X(1)A(1) ground state of H2S2+. The lifetimes of the 3e(1/2) and 5e(1/2) levels of the 2p ionized molecule are found to be 64 and 74 meV, respectively. This unambiguous determination of the lifetime difference of 10+/-1 meV is only possible as the 4e(1/2)-->X(1)A(1)(2b(1)(-2)) decay channel that overlaps the 5e(1/2)-->X(1)A(1)(2b(1)(-2)) channel is practically suppressed in Auger decay in H2S. The lifetime difference is confirmed by ab initio calculations. A theoretical analysis shows that it results from the mutual orientation of the core hole in the intermediate states and the valence electron density in the sulfur 3p orbitals. Both are strongly influenced by the chemical bond. Thus the observed effect is the direct result of a fundamental property of molecular electronic structure.
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10.
  • Burmeister, F, et al. (författare)
  • Nonadiabatic effects in photoelectron spectra of HCl and DCl. I. Experiment
  • 2002
  • Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 65:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The HCl inner-valence photoelectron band at 26 eV binding energy has been recorded at high resolution. Discrete peaks arising from at least two separate vibrational progressions are superimposed on the broad continuum. Fano profiles are visible in one of the progressions. This indicates interference between superimposed electronic states, where weak avoided crossing allows two adiabatic states to couple. In the isotopic DCl molecular spectrum, the discrete lines are less pronounced, due to slower dissociation and therefore less coupling between the continuum and the bound state.
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  • Resultat 1-10 av 29

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