661 research outputs found
Dielectronic Resonance Method for Measuring Isotope Shifts
Longstanding problems in the comparison of very accurate hyperfine-shift
measurements to theory were partly overcome by precise measurements on
few-electron highly-charged ions. Still the agreement between theory and
experiment is unsatisfactory. In this paper, we present a radically new way of
precisely measuring hyperfine shifts, and demonstrate its effectiveness in the
case of the hyperfine shift of and in
. It is based on the precise detection of dielectronic
resonances that occur in electron-ion recombination at very low energy. This
allows us to determine the hyperfine constant to around 0.6 meV accuracy which
is on the order of 10%
Reply to Comment by M. B. J. Meinders, L. H. Tjeng, and G. A. Sawatzky, Physical Review Letters 73 (1994) 2937
Depletion of density of states near Fermi energy induced by disorder and electron correlation in alloys
We have performed high resolution photoemission study of substitutionally
disordered alloys Cu-Pt, Cu-Pd, Cu-Ni, and Pd-Pt. The ratios between alloy
spectra and pure metal spectra are found to have dips at the Fermi level when
the residual resistivity is high and when rather strong repulsive
electron-electron interaction is expected. This is in accordance with Altshuler
and Aronov's model which predicts depletion of density of states at the Fermi
level when both disorder and electron correlation are present.Comment: 1 tex file and 4 ps file
Resonant Auger spectroscopy at the L2,3 shake-up thresholds as a probe of electron correlation effects in nickel
The excitation energy dependence of the three-hole satellites in the
L3-M4,5M4,5 and L2-M4,5M4,5 Auger spectra of nickel metal has been measured
using synchrotron radiation. The satellite behavior in the non-radiative
emission spectra at the L3 and L2 thresholds is compared and the influence of
the Coster-Kronig channel explored. The three-hole satellite intensity at the
L3 Auger emission line reveals a peak structure at 5 eV above the L3 threshold
attributed to resonant processes at the 2p53d9 shake-up threshold. This is
discussed in connection with the 6-eV feature in the x-ray absorption spectrum.Comment: 8 pages, 4 figures; http://prb.aps.org/abstract/PRB/v58/i7/p3677_
CYP2C8 status of patients with malaria influences selection of Plasmodium falciparum pfmdr1 Alleles after Amodiaquine-Artesunate treatment
info:eu-repo/semantics/publishedVersio
Position controlled self-catalyzed growth of GaAs nanowires by molecular beam epitaxy
GaAs nanowires are grown by molecular beam epitaxy using a self-catalyzed,
Ga-assisted growth technique. Position control is achieved by nano-patterning a
SiO2 layer with arrays of holes with a hole diameter of 85 nm and a hole pitch
varying between 200 nm and 2 \mum. Gallium droplets form preferentially at the
etched holes acting as catalyst for the nanowire growth. The nanowires have
hexagonal cross-sections with {110} side facets and crystallize predominantly
in zincblende. The interdistance dependence of the nanowire growth rate
indicates a change of the III/V ratio towards As-rich conditions for large hole
distances inhibiting NW growth.Comment: 9 pages, 4 figure
Intramolecular vibronic dynamics in molecular solids: C60
Vibronic coupling in solid C60 has been investigated with a combination of resonant photoemission spectroscopy (RPES) and resonant inelastic x-ray scattering (RIXS). Excitation as a function of energy within the lowest unoccupied molecular orbital resonance yielded strong oscillations in intensity and dispersion in RPES, and a strong inelastic component in RIXS. Reconciling these two observations establishes that vibronic coupling in this core hole excitation leads to predominantly inelastic scattering and localization of the excited vibrations on the molecule on a femtosecond time scale. The coupling extends throughout the widths of the frontier valence bands.
Isotope shift in the electron affinity of chlorine
The specific mass shift in the electron affinity between ^{35}Cl and ^{37}Cl
has been determined by tunable laser photodetachment spectroscopy to be
-0.51(14) GHz. The isotope shift was observed as a difference in the onset of
the photodetachment process for the two isotopes. In addition, the electron
affinity of Cl was found to be 29138.59(22) cm^{-1}, giving a factor of 2
improvement in the accuracy over earlier measurements. Many-body calculations
including lowest-order correlation effects demonstrates the sensitivity of the
specific mass shift and show that the inclusion of higher-order correlation
effects would be necessary for a quantitative description.Comment: 16 pages, 6 figures, LaTeX2e, amsmat
Transition from a molecular to a metallic adsorbate system: Core-hole creation and decay dynamics for CO coordinated to Pd
Two alternative methods to experimentally monitor the development of a CO-adsorption system that gradually changes from molecular to metallic are presented: firstly by adsorption of CO on Pd islands of increasing size deposited under UHV conditions, and secondly by growth of a Pd carbonyl-like species, formed by Pd deposition in CO atmosphere. The change in screening dynamics as a function of the number of metal atoms was investigated, using x-ray photoelectron spectroscopy, x-ray absorption spectroscopy, and core-hole-decay techniques. For CO adsorbed on UHV-deposited islands, the electronic properties of the whole CO-Pd complex is strongly dependent on island size and CO coverage: large amounts of CO result in a reduced screening ability, and small effects characteristic of molecular systems can be detected even for islands containing about 100 Pd atoms. If about half of the CO overlayer is desorbed, the CO-Pd complex exhibits a relaxation upon core ionization that is nearly as efficient as for metallic systems, even for the smallest islands (of the order of 10 Pd atoms). The growth of the carbonyl-like compound proceeds via formation of Pd-Pd bonds and has a relatively well-defined local structure. It is demonstrated that the properties of this compound approach those of an extended system for increasing coverages, and it may therefore also serve as an important link between a carbonyl and CO adsorbed on a metallic surface. A brief discussion is also given in which the results are discussed in terms of electronic properties of the thin alumina film versus bulk alumina and the applicability of the former to the construction of model catalysts
Interaction of CO with Pd clusters supported on a thin alumina film
The adsorption of CO on Pd particles supported on a thin alumina film has been studied employing high resolution xâray photoelectron spectroscopy (XPS) and xâray absorption spectroscopy (XAS), and of special interest was the COâPd interaction as a function of island size and CO coverage. CO saturation at 90 K leads to an overlayer characterized by a rather weak COâPd hybridization as manifested by the core ionized and core excited states. The interaction strength gradually increases with island size. Desorption of parts of the overlayer results in CO more strongly interacting with the Pd islands. A comparison between the XPS and XAS energies yields a behavior indistinguishable from metallic systems for islands larger than 15 Ă
, i.e., the XPS binding energy appears near the xâray absorption onset. For the smallest islands (5 Ă
), a CO coverage dependent reversal of the XPSâXAS energy relation was observed, indicating a drastic change in the screening ability of the COâPd complex
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