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  • 1
    Electronic Resource
    Electronic Resource
    Antidotes to organophosphate poisoning. 2. Thiadiazole-5-carboxaldoximes (1979)
    s.l. : American Chemical Society
    Journal of medicinal chemistry 22 (1979), S. 1306-1313 
    Details
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jm00197a006
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  • 2
    Electronic Resource
    Electronic Resource
    On the role of atomic oxygen in the etching of organic polymers in a radio-frequency oxygen discharge (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 47-54 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The kinetics of rise and decay of ground-state atomic oxygen was investigated in a low-pressure O2 radio-frequency discharge. The ground state of O was monitored using laser-induced-fluorescence spectroscopy. The discharge was operated in two modes: a continuous mode and a pulsed mode. Typical discharge settings are rf power of 100 W, a pressure of 10 Pa, and a gas flow of 10 sccm. Using a pulsed mode the behavior of the O density was determined in a pure O2 discharge with no reaction products, and in a discharge during etching of organic polymers. Production and loss mechanisms for O in a pure O2 discharge are discussed. For an O2 discharge during etching of resist it is found that under the given experimental conditions atomic oxygen does not play a significant role in the chemical etch mechanisms involved. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360630
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  • 3
    Electronic Resource
    Electronic Resource
    Power dissipation measurements in a low-pressure N2 radio-frequency discharge (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 738-746 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Energy-flux density measurements using silicon substrates were performed on various parts of a parallel-plate etch reactor in contact with a low-pressure nitrogen radio-frequency discharge. The energy flux consists of contributions of ions, electrons, atoms, photons, and excited particles. Experimental results on the reaction kinetics of N+2 and atomic oxygen, and some additional model calculations of the excitation rates of molecular nitrogen (N2 X 1Σ+g) to excited electronic states were used to determine the rates of ionization and dissociation, and of vibrational, rotational, translational, and electronic excitation of molecular nitrogen. On the basis of these rates the contribution of various particles to the measured energy flux density on the powered and grounded electrode is discussed. It is shown that for a nitrogen discharge at a pressure of 30 Pa and a rf power setting of 300 W the energy flux density of the energetic particles, which are ions and energetic neutrals formed by charge-exchange and elastic collisions in the sheath, accounts for 93% of the measured energy flux on the powered electrode. The remaining energy flux density is caused by recombination of atomic nitrogen and fluxes of thermal electrons, photons and excited particles. The contributions of thermal electrons in the plasma and the acceleration of secondary electrons and ions in the sheaths to the power dissipation of the rf discharge were determined from experimental results and some additional model calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357819
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  • 4
    Electronic Resource
    Electronic Resource
    Ion-induced etching of organic polymers in argon and oxygen radio-frequency plasmas (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 758-769 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The authors have studied the etching of novolac-based photoresist, polyimide, and polymethylmethacrylate in oxygen and argon rf plasmas at pressures between 0.3 and 10 Pa in a reactive-ion-etching (RIE) reactor. Energy-flux density measurements on the powered electrode were performed under experimental conditions identical to those used during the etch experiments. In both plasmas the etch rate of these polymers depends proportionally on the energy-flux density of the impinging energetic particles, which are the ions and the energetic neutrals formed by elastic and charge-exchange collisions between ions and neutral gas particles in the sheath. In oxygen and argon plasmas under RIE conditions the etch mechanism of these polymers is ion induced. Average values of the overall carbon yield were determined as a function of the average energy of the impinging energetic particles between 50 and 650 eV and as a function of the angle of incidence. The results obtained in oxygen plasmas were compared with those obtained in argon plasmas and the chemical enhancement in the presence of oxygen is determined. By monitoring changes in gas pressure and energy-flux density on the substrate due to polymer etching, details about the oxidation reaction and the identity of the oxidizing particles in the plasma have been obtained. It is shown that the oxidation reaction occurs mainly with molecular oxygen and for the larger part on the polymer surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356481
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  • 5
    Electronic Resource
    Electronic Resource
    Reaction kinetics of CH radical during etching of polymers in argon and oxygen rf plasmas (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 5799-5805 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: During sputtering of polymethylmethacrylate in a low-pressure argon rf plasma, the density and the reaction kinetics of ground-state methylidyne (CH radical) were determined by laser induced fluorescence spectroscopy (LIF). For a plasma in a steady-state condition at 10 Pa and 100 W, the density of CH in the bulk of the plasma was 6.8×1010 cm−3. By pulsing the rf power, the production rate of CH was determined to be 5.1×1013 cm−3 s−1. This production rate was found to be independent of CH density and time after the plasma had been switched on, indicating that CH is not formed in the gas phase, but is sputtered from the substrate. A model, taking diffusion of CH from the substrate into the plasma and chemical reactions in the gas phase into account, has been set up to calculate the CH flux from the substrate surface. The calculated rise curve of CH could be fitted to the measured data with a diffusion coefficient D=1800 cm2 s−1 and an overall reaction rate coefficient k=55 s−1. These data have been used to calculate the total CH flux from the substrate. From this CH flux and the ion current density on the powered electrode, the CH yield was determined to be 0.02 CH radicals per ion, indicating that CH is not the main sputtered species since the overall carbon yield is 4.8 per ion. In an oxygen plasma the CH density is below the detection limit of LIF due to a high overall reaction rate coefficient with O and O2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350474
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  • 6
    Electronic Resource
    Electronic Resource
    Excitation mechanisms of oxygen atoms in a low pressure O2 radio-frequency plasma (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5278-5281 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using a low-pressure reactive ion etching reactor in a pulsed radio-frequency (rf) power mode the rise time of the plasma induced emission of O at 777 and 844 nm was monitored on a ms time scale. With a two-photon excitation scheme the rise time of the oxygen atom ground state concentration was followed by measuring the laser induced fluorescence (LIF) at 844 nm. An absolute density measurement was performed by comparing the LIF signal in the reactor to the LIF signal of a known concentration of O in a microwave discharge. Using these time resolved measurements the reliability of optical emission actinometry in low pressure O2 rf plasmas for a determination of relative atomic oxygen densities was examined. By comparing the rise times with the ignition time of the plasma it is concluded that both emission lines are caused by dissociative excitation. The consequences for the applicability of actinometry will be discussed. A comparison of experimental emission intensities to calculated ones suggests that highly energetic (e.g., secondary) electrons are responsible for the dissociative excitation of O2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350237
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  • 7
    Electronic Resource
    Electronic Resource
    Tabulation of the theoretical band-to-band luminescence spectra of heavily doped GaAs and application to experimental n-type GaAs spectra (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5819-5826 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have calculated the expressions for band-to-band luminescence given by Lasher and Stern for heavily doped GaAs. The resulting values in the case of no k selection rule are tabulated. A comparison between theory and experiment is made, which shows that good agreement can be obtained. From this comparison can be concluded that the band-to-band luminescence in heavily doped n-type GaAs is governed by transitions without k selection, whereas in moderately doped GaAs the transitions are without k selection at low temperatures but with k selection at room temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346954
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  • 8
    Electronic Resource
    Electronic Resource
    The time evolution of the ion density and the gas temperature in pulsed radio frequency plasmas (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 5792-5798 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The kinetics of the formation and decay of pulsed nitrogen rf plasmas have been investigated with time and spatially resolved optical emission and laser induced fluorescence spectroscopy. At a gas pressure of 3 Pa the decay of the N2+ ions, after the power is switched off, is caused by dissociative recombination and ambipolar diffusion to the wall. At higher pressures (30 Pa) the formation of N4+ has to be taken into account. An accurate method to determine the ion density from the second order decay is presented. A numerical model of the time evolution of the ion concentration profile is developed, which renders good agreement with the experimental data. Kinetic measurements of the rotational (Tr) and vibrational (Tv) temperature of N2+ show that Tr and Tv of N2+ are in equilibrium with Tr and Tv of the N2 gas. The vibrational temperature is, however, much higher than the rotational temperature. This observation can be readily explained on the basis of the results of the kinetic measurements. The experimental excitation and cooling rates for the translational, rotational, and vibrational energy levels of the N2 molecules are compared to simulations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350473
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  • 9
    Electronic Resource
    Electronic Resource
    Photoinduced Wolff-Rearrangement of 2-Diazo-1-naphthoquinones: Evidence for the Participation of a Carbene Intermediate (1994)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 116 (1994), S. 11754-11763 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00105a016
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  • 10
    Electronic Resource
    Electronic Resource
    Increased cytokinin levels in transgenic PSAG12–IPT tobacco plants have large direct and indirect effects on leaf senescence, photosynthesis and N partitioning (2000)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 23 (2000), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We studied the impact of delayed leaf senescence on the functioning of plants growing under conditions of nitrogen remobilization. Interactions between cytokinin metabolism, Rubisco and protein levels, photosynthesis and plant nitrogen partitioning were studied in transgenic tobacco (Nicotiana tabacum L.) plants showing delayed leaf senescence through a novel type of enhanced cytokinin syn-thesis, i.e. targeted to senescing leaves and negatively auto-regulated (PSAG12–IPT), thus preventing developmental abnormalities. Plants were grown with growth-limiting nitrogen supply. Compared to the wild-type, endogenous levels of free zeatin (Z)- and Z riboside (ZR)-type cytokinins were increased up to 15-fold (total ZR up to 100-fold) in senescing leaves, and twofold in younger leaves of PSAG12–IPT. In these plants, the senescence-associated declines in N, protein and Rubisco levels and photosynthesis rates were delayed. Senescing leaves accumulated more (15N-labelled) N than younger leaves, associated with reduced shoot N accumulation (–60%) and a partially inverted canopy N profile in PSAG12–IPT plants. While root N accumulation was not affected, N translocation to non-senescing leaves was progressively reduced. We discuss potential consequences of these modified sink–source relations, associated with delayed leaf senescence, for plant productivity and the efficiency of utilization of light and minerals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2000.00544.x
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