We have studied enantiospecific differences in the adsorption of (S)- and (R)-alanine on Cu{531}
R
using
low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy, and near edge X-ray absorption
fine structure (NEXAFS) spectroscopy. At saturation coverage, alanine adsorbs as alaninate forming a
p(1 × 4) superstructure. LEED shows a significantly higher degree of long-range order for the S than for the
R enantiomer. Also carbon K-edge NEXAFS spectra show differences between (S)- and (R)-alanine in the
variations of the π resonance when the linear polarization vector is rotated within the surface plane. This
indicates differences in the local adsorption geometries of the molecules, most likely caused by the interaction
between the methyl group and the metal surface and/or intermolecular hydrogen bonds. Comparison with
model calculations and additional information from LEED and photoelectron spectroscopy suggest that both
enantiomers of alaninate adsorb in two different orientations associated with triangular adsorption sites on
{110} and {311} microfacets of the Cu{531} surface. The experimental data are ambiguous as to the exact
difference between the local geometries of the two enantiomers. In one of two models that fit the data equally
well, significantly more (R)-alaninate molecules are adsorbed on {110} sites than on {311} sites whereas for
(S)-alaninate the numbers are equal. The enantiospecific differences found in these experiments are much
more pronounced than those reported from other ultrahigh vacuum techniques applied to similar systems.
Carbonaceous deposits produced on Ru-capped multilayer mirrors under extreme ultra violet irradiation in the presence of adventitious gaseous hydrocarbons are a major obstacle to process implementation of EUV lithography. Here, by means of synchrotron radiation and laboratory measurements we show how carbon contamination occurs as a result of photoelectron-induced surface chemistry. We also demonstrate how a device based on an oxygen ion conducting solid electrolyte can act as a sensitive and reproducible sensor for detection of trace amounts of hydrocarbons in high vacuum environments.
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