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111.
M. Bertino W. Steinhögl H. Range F. Hofmann G. Witte E. Hulpke Ch. Wöll 《Applied Physics A: Materials Science & Processing》1996,62(2):95-101
The adsorption of N2 molecules on Ni(110) has been investigated by high-resolution He-atom energy-loss spectroscopy. Two external vibrations in the subthermal (< 30 meV) energy regime at 5.75 and 4.5 meV have been observed and are shown to imply the existence of two different adsorption sites, which are assigned to an on-top and a bridge-site. This finding is at variance with the interpretation of data from electron energy loss spectroscopy and InfraRed (IR) spectroscopy, where only one mode of the internal stretch vibration v1 at frequencies is observed for the chemisorbed nitrogen molecules. A reanalysis of previously published high-resolution IR data reveals that the presence of the second unexpected adsorbate species correlates with a feature in the IR spectra, which previously has been assigned to N2 molecules adsorbed at defect sites. These findings reveal that in this case the external vibrations are significantly more sensitive to different adsorption sites than the internal vibration, the latter exhibiting a difference between on-top and bridge sites of less than 6 cm–1. 相似文献
112.
We performed measurements of gettering efficiencies for Cu in silicon wafers with competing gettering sites. Epitaxial wafers
(p/p+) boron-doped with a polysilicon back side allowed us to compare p+ gettering with polysilicon gettering. We further
measured metal distributions in p+/p- epitaxial test wafers, with the p- substrate wafers pretreated for oxygen precipitation
to compare p+ gettering with oxygen precipitate gettering. Our test started with a reproducible spin-on contamination in the
1012 atoms/cm2 range, followed by thermal treatment in order to redistribute the metallic impurity. Wafers were then analyzed by a novel
wet chemical layer-by-layer etching technique in combination with inductively coupled plasma mass spectrometry. This led to
“stratigraphical” concentration profiles of the impurity, with typical detection limits of 5–10×1012 atoms/cm3. Twenty-five percent of the total Cu contamination in the p/p+/poly wafer was found in the p+ layer, whilst 75% was gettered
by the polysilicon. Obviously, polysilicon exhibits a stronger gettering than p+ silicon, but due to the large distance from
the front surface, polysilicon was less effective in reducing impurities from the front side of a wafer compared with p+ gettering.
An epitaxial layer p+ on top of p- substrates with oxygen precipitates gettered 50% of the total Cu; while the other 50% of
the Cu was measured in the p- substrate wafer with oxygen precipitates. Without oxygen precipitates, 100% of the spiked Cu
contamination was detected inside the p+ layer. Gettering by oxygen precipitates thus occurs in the same temperature range
as that where p+ silicon begins to getter Cu.
Received: 3 September 2001 / Accepted: 17 October 2001 / Published online: 27 March 2002 相似文献
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115.
P.S.L. BoothG.R. Court B. CravenR. Gamet P.J. HaymanJ.R. Holt A.P. HuftonJ.N. Jackson J.H. NoremW.H. Range 《Physics letters. [Part B]》1972
The polarized target asymmetry parameter has been measured for single πo photoproduction from hydrogen at 4 GeV and values of four-momentum transfer squared between −0.15 (GeV/c)2 and −1.8 (GeV/c)2. 相似文献
116.
K. -J. Range H. Bergmann G. Lagaly C. Mahr W. Brügel 《Colloid and polymer science》1973,251(7):509-520
Ohne Zusammenfassung 相似文献
117.
P.S.L. Booth L.J. Carroll J.R. Holt J.N. Jackson W.H. Range K.A. Sprakes J.R. Wormald 《Nuclear Physics B》1974,71(2):211-216
Differential cross sections for the process γp → pη have been measuredd at c.m. angles of 28°, 35° and 42° at incident energies between 2 GeV and 2.8 GeV. Data from an earlier experiment below 2 GeV have been re-analysed and corrected. The whole set of data is compared with the form (s?M2)2 dσ/dt, which fits data at higher energies. There is good agreement above 2 GeV, particularly at the largest angle, but strong departures below. 相似文献
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120.
Sibert R Josowicz M Porcelli F Veglia G Range K Barry BA 《Journal of the American Chemical Society》2007,129(14):4393-4400
Proton-coupled electron-transfer reactions are central to enzymatic mechanism in many proteins. In several enzymes, essential electron-transfer reactions involve oxidation and reduction of tyrosine side chains. For these redox-active tyrosines, proton transfer couples with electron transfer, because the phenolic pKA of the tyrosine is altered by changes in the tyrosine redox state. To develop an experimentally tractable peptide system in which the effect of proton and electron coupling can be investigated, we have designed a novel amino acid sequence that contains one tyrosine residue. The tyrosine can be oxidized by ultraviolet photolysis or electrochemical methods and has a potential cross-strand interaction with a histidine residue. NMR spectroscopy shows that the peptide forms a beta-hairpin with several interstrand dipolar contacts between the histidine and tyrosine side chains. The effect of the cross-strand interaction was probed by electron paramagnetic resonance and electrochemistry. The data are consistent with an increase in histidine pKA when the tyrosine is oxidized; the effect of this thermodynamic coupling is to increase tyrosyl radical yield at low pH. The coupling mechanism is attributed to an interstrand pi-cation interaction, which stabilizes the tyrosyl radical. A similar interaction between histidine and tyrosine in enzymes provides a regulatory mechanism for enzymatic electron-transfer reactions. 相似文献