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- Stolte, W.C., et al.
(author)
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The K-shell Auger decay of atomic oxygen
- 1997
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In: Journal of Physics B: Atomic, Molecular and Optical Physics. - 0953-4075. ; 30:20, s. 4489-4497
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Journal article (peer-reviewed)abstract
- Relative photoionization cross sections for O+ and O2+ produced by the Auger decay of a 1s hole in atomic oxygen were measured by using synchrotron radiation between 525 and 553 eV. Energies and quantum defects of the members of the two Rydberg series converging to [1s]2s22p4(4P) and [1s]2s22p4(2P) ionization thresholds were determined. In addition, the 2P and 4P ionization thresholds were calculated from the two Rydberg series. The 182 meV resolution of the monochromator allowed a detailed study over both thresholds revealing evidence for post-collision interaction and allowing a comparison of the ionization continuum above both 2P and 4P thresholds with that of the ionization continuum above the Ar L2 and L3 edges. This comparison indicates that the lifetimes of the Ar(2p) and O(1s) hole states are approximately the same.
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- Lu, W., et al.
(author)
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Nondestructive determination of sheet carrier density in pseudomorphic AlGaAs/InGaAs/GaAs high electron mobility transistor structures by room-temperature photoluminescence spectra
- 1998
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In: Journal of Physics D-Applied Physics. ; 31:2, s. 159-164
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Journal article (peer-reviewed)abstract
- This paper describes a nondestructive method to determine the sheet carrier density of pseudomorphic high electron mobility transistor structures by fitting the room-temperature photoluminescence (PL) spectra. The sheet carrier densities determined were in sufficiently good agreement with values determined by Hall measurements for different samples with different mole fractions, delta-doping densities and well widths. For single-doped AlGaAs/InGaAs quantum wells, the dominant emission is the transitions from the first electron subband to the first heavy hole subband, from the first electron subband to the second heavy hole subband, and from the second electron subband to the first heavy hole subband.
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- Pradier, C.M., et al.
(author)
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NO reduction by isobutene, in the presence of oxygen, on platinum and copper : a comparative study
- 1996
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In: Catalysis Today. - : Elsevier BV. - 0920-5861 .- 1873-4308. ; 29:1-4, s. 59-65
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Journal article (peer-reviewed)abstract
- The reaction of NO, oxygen and isobutene was studied under conditions close to stoichiometric, on a platinum and on a copper disk in order to better understand the role of each metal, free of any support and dispersion effects. The products of the reaction were analysed by mass spectrometry and an XPS characterization of the surface was carried out at different stages of the reaction. A correlation between the catalytic activity for NO conversion and the presence of adsorbed intermediates has been clearly demonstrated on platinum. On copper, a redox cycle of the metal is necessary to activate the catalyst. On platinum, oxygen is necessary to initiate the reaction, clean the surface and form reactive intermediates; the reaction is strongly sensitive to oxygen concentration, whereas on copper, oxygen does not directly participate in the reaction mechanism.
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- Zhu, J. W., et al.
(author)
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Reductase specificity and the ratio regulation of E/Z isomers in pheromone biosynthesis of the European corn borer, Ostrinia nubilalis (Lepidoptera Pyralidae)
- 1996
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In: Insect Biochemistry and Molecular Biology. - : Elsevier BV. - 0965-1748. ; 26:2, s. 171-176
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Journal article (peer-reviewed)abstract
- Species specificity of moth sex pheromones is in many cases achieved by means of specific blends rather than by specific components. Two pheromone strains of the European corn borer, Ostrinia nubilalis, use (E)- and (Z)-11-tetradecenyl acetate in different ratios as their pheromone, but show the same ratio of the pheromone precursors (70:30 E/Z-11-tetradecenoic acid). The hypothesis that the ratio of the pheromone components in the two strains and their hybrids is controlled by the specificity of the reductase system, responsible for conversion of acid to the corresponding alcohol precursors, was tested. Deuterium-labeled alcohols, aldehydes and fatty acids corresponding to the two pheromone components were topically applied to the pheromone glands in different ratios and their selective incorporation into pheromone components was determined by gas chromatography with mass selective detection. Acetylation of the (E)- and (Z)-11-tetradecenols was unselective, whereas the corresponding aldehydes and acids were selectively incorporated into the pheromone components. Z strain females selectively metabolized the Z-isomers whereas E strain females converted the E-isomers. The E strain being the most selective of the two strains. Hybrids converted both geometric isomers. The relative conversion rate of both E- and Z-isomers of all tetradecenoic acids with the double bond in positions from 7-12, was also determined. In addition to the Δ11-isomers, the E strain females converted (E)-8-tetradecenoic acid into acetate and the Z strain females converted (E)-12-tetradecenoic acid. None of these substrates occur naturally in the pheromone gland, but (E)-12-tetradecenyl acetate is a pheromone component of the Asian corn borer O. furnacalis. Thus the possibility for conversion of (E)-12-tetradecenoic acid to acetate in the Z strain, as well as the earlier reported conversion of (Z)-11-tetradecenoic acid to acetate in O. furnacalis, suggests that O. furnacalis is closest related to the Z strain of O. nubilalis.
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