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J. R. Doyle - One of the best experts on this subject based on the ideXlab platform.

  • hydrogen release kinetics during reactive magnetron sputter deposition of a si h an Isotope Labeling Study
    Journal of Applied Physics, 1994
    Co-Authors: John R. Abelson, L. Mandrell, J. R. Doyle
    Abstract:

    The release of molecular hydrogen from the growing surface of hydrogenated amorphous silicon films is determined using an Isotope labelling technique. The results demonstrate that surface‐bonded H atoms are readily abstracted by atomic hydrogen arriving from the gas phase. The films are deposited by dc reactive magnetron sputtering of a silicon target in an argon‐hydrogen atmosphere. To achieve Isotope Labeling, we first deposit a deuterated amorphous silicon film, then commence growth of hydrogenated amorphous silicon and measure the transient release of HD and D2 from the growing surface using mass spectrometry. Release occurs when the supply of reactive hydrogen in the growth flux exceeds the incorporation rate into the film, and is observed under all experimental conditions. The net rate of H incorporation is known from ex situ measurements of film growth rate and hydrogen content. We combine the H release and incorporation data in a mass balance argument to determine the H‐surface kinetics. Under con...

  • Hydrogen release kinetics during reactive magnetron sputter deposition of a‐Si:H: An Isotope Labeling Study
    Journal of Applied Physics, 1994
    Co-Authors: John R. Abelson, L. Mandrell, J. R. Doyle
    Abstract:

    The release of molecular hydrogen from the growing surface of hydrogenated amorphous silicon films is determined using an Isotope labelling technique. The results demonstrate that surface‐bonded H atoms are readily abstracted by atomic hydrogen arriving from the gas phase. The films are deposited by dc reactive magnetron sputtering of a silicon target in an argon‐hydrogen atmosphere. To achieve Isotope Labeling, we first deposit a deuterated amorphous silicon film, then commence growth of hydrogenated amorphous silicon and measure the transient release of HD and D2 from the growing surface using mass spectrometry. Release occurs when the supply of reactive hydrogen in the growth flux exceeds the incorporation rate into the film, and is observed under all experimental conditions. The net rate of H incorporation is known from ex situ measurements of film growth rate and hydrogen content. We combine the H release and incorporation data in a mass balance argument to determine the H‐surface kinetics. Under con...

John R. Abelson - One of the best experts on this subject based on the ideXlab platform.

  • hydrogen release kinetics during reactive magnetron sputter deposition of a si h an Isotope Labeling Study
    Journal of Applied Physics, 1994
    Co-Authors: John R. Abelson, L. Mandrell, J. R. Doyle
    Abstract:

    The release of molecular hydrogen from the growing surface of hydrogenated amorphous silicon films is determined using an Isotope labelling technique. The results demonstrate that surface‐bonded H atoms are readily abstracted by atomic hydrogen arriving from the gas phase. The films are deposited by dc reactive magnetron sputtering of a silicon target in an argon‐hydrogen atmosphere. To achieve Isotope Labeling, we first deposit a deuterated amorphous silicon film, then commence growth of hydrogenated amorphous silicon and measure the transient release of HD and D2 from the growing surface using mass spectrometry. Release occurs when the supply of reactive hydrogen in the growth flux exceeds the incorporation rate into the film, and is observed under all experimental conditions. The net rate of H incorporation is known from ex situ measurements of film growth rate and hydrogen content. We combine the H release and incorporation data in a mass balance argument to determine the H‐surface kinetics. Under con...

  • Hydrogen release kinetics during reactive magnetron sputter deposition of a‐Si:H: An Isotope Labeling Study
    Journal of Applied Physics, 1994
    Co-Authors: John R. Abelson, L. Mandrell, J. R. Doyle
    Abstract:

    The release of molecular hydrogen from the growing surface of hydrogenated amorphous silicon films is determined using an Isotope labelling technique. The results demonstrate that surface‐bonded H atoms are readily abstracted by atomic hydrogen arriving from the gas phase. The films are deposited by dc reactive magnetron sputtering of a silicon target in an argon‐hydrogen atmosphere. To achieve Isotope Labeling, we first deposit a deuterated amorphous silicon film, then commence growth of hydrogenated amorphous silicon and measure the transient release of HD and D2 from the growing surface using mass spectrometry. Release occurs when the supply of reactive hydrogen in the growth flux exceeds the incorporation rate into the film, and is observed under all experimental conditions. The net rate of H incorporation is known from ex situ measurements of film growth rate and hydrogen content. We combine the H release and incorporation data in a mass balance argument to determine the H‐surface kinetics. Under con...

L. Mandrell - One of the best experts on this subject based on the ideXlab platform.

  • hydrogen release kinetics during reactive magnetron sputter deposition of a si h an Isotope Labeling Study
    Journal of Applied Physics, 1994
    Co-Authors: John R. Abelson, L. Mandrell, J. R. Doyle
    Abstract:

    The release of molecular hydrogen from the growing surface of hydrogenated amorphous silicon films is determined using an Isotope labelling technique. The results demonstrate that surface‐bonded H atoms are readily abstracted by atomic hydrogen arriving from the gas phase. The films are deposited by dc reactive magnetron sputtering of a silicon target in an argon‐hydrogen atmosphere. To achieve Isotope Labeling, we first deposit a deuterated amorphous silicon film, then commence growth of hydrogenated amorphous silicon and measure the transient release of HD and D2 from the growing surface using mass spectrometry. Release occurs when the supply of reactive hydrogen in the growth flux exceeds the incorporation rate into the film, and is observed under all experimental conditions. The net rate of H incorporation is known from ex situ measurements of film growth rate and hydrogen content. We combine the H release and incorporation data in a mass balance argument to determine the H‐surface kinetics. Under con...

  • Hydrogen release kinetics during reactive magnetron sputter deposition of a‐Si:H: An Isotope Labeling Study
    Journal of Applied Physics, 1994
    Co-Authors: John R. Abelson, L. Mandrell, J. R. Doyle
    Abstract:

    The release of molecular hydrogen from the growing surface of hydrogenated amorphous silicon films is determined using an Isotope labelling technique. The results demonstrate that surface‐bonded H atoms are readily abstracted by atomic hydrogen arriving from the gas phase. The films are deposited by dc reactive magnetron sputtering of a silicon target in an argon‐hydrogen atmosphere. To achieve Isotope Labeling, we first deposit a deuterated amorphous silicon film, then commence growth of hydrogenated amorphous silicon and measure the transient release of HD and D2 from the growing surface using mass spectrometry. Release occurs when the supply of reactive hydrogen in the growth flux exceeds the incorporation rate into the film, and is observed under all experimental conditions. The net rate of H incorporation is known from ex situ measurements of film growth rate and hydrogen content. We combine the H release and incorporation data in a mass balance argument to determine the H‐surface kinetics. Under con...

Steven L. Suib - One of the best experts on this subject based on the ideXlab platform.

  • the role of lattice oxygen in selective benzyl alcohol oxidation using oms 2 catalyst a kinetic and Isotope Labeling Study
    Journal of Catalysis, 2002
    Co-Authors: Vinit D Makwana, Amy R Howell, Steven L. Suib
    Abstract:

    The oxidation of benzyl alcohol by molecular O2 in the liquid phase using a heterogeneous octahedral molecular sieve (OMS) catalyst was studied. Typical batch reactor kinetic data were obtained and fitted to the classical Langmuir–Hinshelwood–Hougen–Watson (LHHW) model as well as to the Mars–van Krevelen (MvK) model of heterogeneously catalyzed reactions. A two-step Mars–van Krevelen model involving an exchange between the gas phase and lattice oxygen was found to give a better fit. This was further corroborated by an oxygen-Isotope-Labeling Study. The changes in the 16O and 18O content of the product water confirm this observation. Kinetic Isotope effects were also evaluated in mechanistic studies. The occurrence of this mechanism in the liquid phase explains the activity and high selectivity of the OMS-2 catalyst for this selective oxidation reaction.

Jack J. Middelburg - One of the best experts on this subject based on the ideXlab platform.

  • Balance between nitrogen assimilation and dissimilation in tidal mudflat sediment: A stable Isotope Labeling Study
    2011
    Co-Authors: Kirstin Dähnke, A. Moneta, Bart Veuger, Karline Soetaert, Jack J. Middelburg
    Abstract:

    Due to intense nitrogen cycling, coastal sediments largely control nutrient export from the coastal region to the adjacent ocean, particularly in a shallow and eutrophic region like the Southern North Sea. Relevant benthic processes include both assimilatory and dissimilatory pathways, but most studies on benthic nitrogen cycling generally deal with either of those and usually focus on only one or two specific processes. As a consequence, the integrated fate of nitrogen in sediments and the associated balance between assimilatory versus dissimilatory processes has remained unstudied. We conducted a 15N-Labeling experiment in which 15N-labeled ammonium and nitrate were added to tidal flat sediment. Analysis of 15N in bulk- and KCl-extracted sediment and ammonium, nitrate, and N2 in pore water allowed us to quantify all major assimilatory and dissimilatory processes in the sediment. Results showed that, barring considerable denitrification, assimilatory processes clearly dominated nitrogen turnover, with comparable impact of bacteria and benthic microalgae, whereas nitrification and dissimilatory nitrate reduction to ammonium (DNRA) were found to be of subordinate role. By combining data with a zero-dimensional N-cycle model, it became apparent that physical processes that cannot be deduced from flux rates alone also play a significant role in sedimentary nitrogen cycling. These findings further underscore the force of combined approaches that integrate observational and modeling results.

  • Carbon fluxes in natural plankton communities under elevated CO 2 levels: a stable Isotope Labeling Study
    2010
    Co-Authors: A. De Kluijver, Karline Soetaert, Kai Georg Schulz, Ulf Riebesell, Richard G. J. Bellerby, Jack J. Middelburg
    Abstract:

    Abstract. The potential impact of rising carbon dioxide (CO2) on carbon fluxes in natural plankton communities was investigated during the 2005 PeECE III mesocosm Study in Bergen, Norway. Triplicate mesocosms, in which a phytoplankton bloom was induced by nutrient addition, were incubated with 1×(~350 μatm), 2×(~700 μatm), and 3× present day CO2(~1050 μatm) levels for 3 weeks. 13C labeled bicarbonate was added to all mesocosms to follow the transfer of carbon from dissolved inorganic carbon (DIC) into phytoplankton and subsequently heterotrophic bacteria, zooplankton, and settling particles. Isotope ratios of polar lipid fatty acids (PLFA) were used to infer the biomass and production of phytoplankton and bacteria. Phytoplankton PLFA were enriched within one day after label addition, while it took another 3 days before bacteria showed substantial enrichment. Group-specific primary production measurements revealed that coccolithophores grew faster than green algae and diatoms. Elevated CO2 had a significant positive effect on post-bloom biomass of green algae, diatoms, and bacteria. A simple model based on measured Isotope ratios of phytoplankton and bacteria revealed that CO2 had no significant effect on the carbon transfer efficiency from phytoplankton to bacteria. There was no indication of enhanced settling based on Isotope mixing models during the phytoplankton bloom. Our results suggest that CO2 effects are most pronounced in the post-bloom phase, under nutrient limitation.

  • The trophic significance of bacterial carbon in a marine intertidal sediment: Results of an in situ stable Isotope Labeling Study
    Limnology and Oceanography, 2006
    Co-Authors: Dick Van Oevelen, Karline Soetaert, Leon Moodley, Jack J. Middelburg
    Abstract:

    We report the results of an in situ tracer experiment in an intertidal sediment, where bacterial carbon was tagged with stable carbon–Isotope label, after the injection of 13C-glucose. The appearance of label in bacteria (based on label incorporation in bacteria-specific, phospholipid-derived fatty acids) and subsequent transfer to meiobenthos (group level) and macrobenthos (species level) was followed for 36 days. The label dynamics of benthic taxa were either fitted with a simple-Isotope model or evaluated against enrichment in bacteria, to derive the importance of bacterially derived carbon for the meiobenthos and macrobenthos. Although selective uptake of bacteria was evident, as 2.4 times more bacterial carbon was grazed as expected from indiscriminate feeding, bacterial carbon accounted on average for only 0.08 and 0.11 of the carbon requirements of meiobenthic and macrobenthic taxa, respectively. Additionally, the contribution of bacterial carbon to total carbon requirements did not depend on the living/feeding depth in the sediment or organism size (evaluated over a size range of four orders of magnitude). The observed overall low contribution of bacterial carbon implies that most intertidal benthic fauna depend primarily on other carbon resources that may assert a stronger control on the structure of intertidal-sediment communities.