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  • 1
    Electronic Resource
    Electronic Resource
    Microcalorimetric studies of zeolite acidity (1992)
    Springer
    Catalysis letters 12 (1992), S. 201-211 
    Details
    ISSN: 1572-879X
    Keywords: Acidity ; gravimetry ; heat of adsorption ; H-Mordenite ; H-Y ; H-ZSM-5 ; microcalorimetry ; pyridine ; zeolite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The acidity characteristics of H-ZSM-5, H-Mordenite and H-Y zeolite have been studied by microcalorimetric and gravimetric measurements of pyridine adsorption. H-ZSM-5 and H-Mordenite have Brønsted acid sites of primarily homogenous strength, with H-Mordenite having the stronger sites, whereas H-Y zeolite had Brønsted sites of varying strength. The effects of Na exchange level in H-Y zeolite and high temperature calcination for H-Mordenite have also been examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00767202
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Thermogravimetric and microcalorimetric studies of ZSM-5 acidity (1993)
    Springer
    Catalysis letters 18 (1993), S. 183-192 
    Details
    ISSN: 1572-879X
    Keywords: Acidity ; zeolites ; microcalorimetry ; thermogravimetry ; pyridine adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The combination of thermogravimetry, microcalorimetry and infrared spectroscopy studies of pyridine adsorption has been used to characterize the acidity of a ZSM-5 catalyst. The majority of the acid sites are Brønsted acid centers associated with framework Al species, with heats of pyridine adsorption equal to 140 kJ/mol. Non-framework Al species in the zeolite sample of this study eliminate an approximately equal number of Brønsted acid sites. These nonframework Al species also produce strong Lewis acid sites with pyridine adsorption heats greater than 140 kJ/mol, as well as weak adsorption sites (e.g., weak Bransted acid sites or hydrogen bonding sites) with heats equal to 90–140 kJ/mol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00769437
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of liming and carbofuran on groundnut yield in sandy soils in Niger (1992)
    Springer
    Nutrient cycling in agroecosystems 33 (1992), S. 203-208 
    Details
    ISSN: 1573-0867
    Keywords: Al ; Arachis hypogaea ; carbofuran ; lime ; nematodes ; pH ; yields
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract One of the constraints to groundnut production in sandy soils of Niger is crop growth variability. In early 1989, a trial on the effect of lime and carbofuran on soil pH, Al toxicity, nematode population and groundnut yield was initiated to study crop growth variability. Groundnut was sown in the 1989 rainy season, followed by pearl millet (Pennisatum glaucum) in the 1989–90 dry season and again groundnut in the 1990–91 rainy, and dry seasons. In 1989 the carbofuran treatment increased the pod yield. Lime application did not change the pH and exchangeable Al+++ contents in the soil and did not increase groundnut yield. In the 1990–91 rainy and dry season, however, the application of 10 t ha−1 of lime increased pH, decreased exchangeable Al+++, improved crop growth and increased the yield of groundnut to the same level as was achieved by the carbofuran treatment. Application of lime did not affect the nematode population, which were reduced by the carbofuran.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01050875
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  • 4
    Electronic Resource
    Electronic Resource
    Role of Scutellonema clathricaudatum in etiology of groundnut growth variability in Niger (1992)
    Springer
    Plant and soil 143 (1992), S. 133-139 
    Details
    ISSN: 1573-5036
    Keywords: aluminium toxicity ; Arachis hypogaea ; crop growth variability ; groundnut ; peanut ; pesticide ; plant-parasitic nematodes ; Niger ; Sahel ; Scutellonema clathricaudatum ; soil pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Variation in crop growth is an important limiting factor for groundnut production in Niger. Populations of Aphelenchoides sp., Ditylenchus sp., Helicotylenchus sp., Hoplolaimus pararobustus, Macroposthonia curvata, Paralongidorus bullatus, Scutellonema clathricaudatum, Telotylenchus indicus and Xiphinema parasetariae have been associated with groundnut crop growth variability. S. clathricaudatum, X. parasetariae and T. indicus were widespread and S. clathricaudatum was most abundant nematode. Population densities of S. clathricaudatum was always higher in the roots of poorly growing, chlorotic and stunted plants than in the roots of apparently healthy plants. A preplant population density of 1.3 S. clathricaudatum cm-3 soil caused (p=0.05) reduction in plant growth of groundnut cv. 55–437. S. clathricaudatum was mainly confined to 0–15 cm soil depth at the time of planting in June and was not found below 45 cm depth at any time during the crop growth period. Soil application of carbofuran (10 kg a.i ha-1) reduced the nematode population densities and resulted in vigorous and uniform crop growth. Higher Al and H-ion concentrations (0.50 meq 100 g-1 soil) also was associated with poorly growing chlorotic seedlings. Symptoms of nematode-caused variable growth were evident 3 to 4 weeks after seedling emergence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00009138
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  • 5
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    Dynamics of dark hollow Gaussian laser pulses in relativistic plasma (2013)
    American Physical Society (APS)
    Details
    Publication Date: 2013-06-26
    Description: Author(s): A. Sharma, S. Misra, S. K. Mishra, and I. Kourakis Optical beams with null central intensity have potential applications in the field of atom optics. The spatial and temporal evolution of a central shadow dark hollow Gaussian (DHG) relativistic laser pulse propagating in a plasma is studied in this article for first principles. A nonlinear Schroding... [Phys. Rev. E 87, 063111] Published Tue Jun 25, 2013
    Keywords: Plasma Physics
    Print ISSN: 1539-3755
    Electronic ISSN: 1550-2376
    Topics: Physics
    Published by American Physical Society (APS)
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    PAPER CURRENT
  • 6
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    Langmuir Probe Measurements in an Inductively Coupled GEC Reference Cell Plasma (1998)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Measurements of electron number density, electron temperature, and electron energy distribution function (EEDF) using a compensated Langmuir probe have been performed on an inductively (transformer ) coupled Gaseous Electronics Conference (GEC) reference cell plasma. The plasma source is operated with CH4, CF4, or their mixtures with argon. The effect of independently driving the electrode supporting the wafer on the probe data is studied. In particular, we find that the plasma structure depends on the phase in addition to the magnitude of the power coupled to the electrode relative to that of the transformer coil. The Langmuir probe is translated in a plane parallel to the electrode to investigate the spatial structure of the plasma. The probe data is also compared with fluid model predictions.
    Keywords: Plasma Physics
    Type: Gaseous Electronics Conference; Oct 19, 1998 - Oct 23, 1998; Hawaii; United States
    Format: text
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  • 7
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    Ion Energy Distributions and their Relative Abundance in Inductively Coupled Plasmas (1998)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Study of kinetics of ions and neutrals produced in high density inductively coupled plasma (ICP) discharges is of great importance for achieving a high degree of plasma assisted deposition and etching. In this paper, we present the ion energy distributions (IEDs) of various ions arriving at the grounded lower electrode. The ions were energy as well as mass analyzed by a combination of electrostatic analyzer-quadrupole mass spectrometer for pure Ar and CF4/Ar mixtures. The measurements have been made at gas pressures ranging from 30 to 100 mTorr. In addition, the IEDs were measured when the wafer-supporting electrode was also rf-powered and the effect of the self-bias was observed in the energy distributions of ions. The shapes of the IEDs are discussed an related to the sheath properties and measured electrical waveforms, as a function of pressure and applied power. Relative ion intensities were obtained by integration of each ion kinetic energy distribution function over its energy range.
    Keywords: Plasma Physics
    Type: Gaseous Electronics Conference; Oct 19, 1998 - Oct 23, 1998; HI; United States
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    NASA TECHNICAL REPORTS
  • 8
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    In situ CF3 Detection in Low Pressure Inductive Discharges by Fourier Transform Infrared Spectroscopy (1998)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: The detection of CF(x) (x=1-3) radicals in low pressure discharges using source gases such as CF4 and CHF3 is of importance to the understanding of their chemical structure and relevance in plasma based etching processes. These radicals are known to contribute to the formation of fluorocarbon polymer films, which affect the selectivity and anisotropy of etching. In this study, we present preliminary results of the quantitative measurement of trifluoromethyl radicals, CF3, in low pressure discharges. The discharge studied here is an inductively (transformer) coupled plasma (ICP) source in the GEC reference cell, operating on pure CF4 at pressures ranging from 10 - 100 mTorr, This plasma source generates higher electron number densities at lower operating pressures than obtainable with the parallel-plate capacitively coupled version of the GEC reference cell. Also, this expanded operating regime is more relevant to new generations of industrial plasma reactors being used by the microelectronics industry. Fourier transform infrared (FTIR) spectroscopy is employed to observe the absorption band of CF3 radicals in the electronic ground state X2Al in the region of 1233-1270/cm. The spectrometer is equipped with a high sensitivity HgCdTe (MCT) detector and has a fixed resolution of 0.125/cm. The CF3 concentrations are measured for a range of operating pressures and discharge power levels.
    Keywords: Plasma Physics
    Type: Gaseous Electronics Conference; Oct 19, 1998 - Oct 23, 1998; Hawaii; United States
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  • 9
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    Langmuir Probe Measurements of Inductively Coupled CHF3/Ar and Ar/CHF3/O2 Plasmas (2000)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: Plasma parameters, such as, electron number density (ne), electron temperature (Te), y electron energy distribution function (EEDF), mean electron energy (Ee), ion number density (ni), and plasma potential (Vp), have been measured by using Langmuir probe in low-pressure (10-50 mTorr) inductively coupled CHF3/Ar and CHF3/Ar/O2 plasmas generated in the GEC cell. The measurements were made at the center of the plasma, keeping the lower electrode grounded, for various CHF3/Ar and Ar/CHF3/O2 mixtures operating at 10-50 mTorr pressures and two input RF power levels, 200 and 300 W. EEDF data show a strong Druyvesteyn distribution with relatively lower number of low energy electrons as compared to a Maxwell distribution and a large electron population with energies higher than the plasma potential. The results further show that at low CHF3 concentrations (less than 50%) the electron number density remains nearly constant with increase in pressure. At higher CHF3 concentrations, however, it decreases with increase in pressure. Plasma potential and electron temperature increase with decrease in pressure and with increase in CHF3 concentration. An analysis of the above observations and mechanisms will be presented.
    Keywords: Plasma Physics
    Type: 53rd Gaseous Electronics Conference; Nov 24, 2000 - Nov 27, 2000; Houston, TX; United States
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  • 10
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    Langmuir Probe Measurements of Inductively Coupled Plasmas in CF4/Ar/O2 Mixtures (2000)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: Fluorocarbon gases, such as CF4, and their mixtures are widely used in contemporary low-pressure and high-density plasma processing techniques. In such plasmas Langmuir probe is one of the most commonly employed diagnostic techniques to obtain electron number density (ne), electron temperature (Te), electron energy distribution function (EEDF), mean electron energy (Ee), ion number density (ni), and plasma potential (Vp). In this paper we report probe data for planar inductively coupled plasmas in CF4/O2/Ar mixtures. By varying the relative concentrations in the mixture, radial profiles of ne, ni, Te, Ee, Vp, EEDF were measured in the mid-plane of the plasma at 10 mTorr and 20 mTorr of gas pressures, and 200 W and 300 W of RF powers. Data show that ne and ni decrease with increase of CF4 content and decrease of gas-pressure but they increase with increase of RF-power, whereas Vp increases with decrease of gas-pressure and remains independent of RF-power. However, they all peak at the center of the plasma and decrease towards the edge while Te follows the other way and increases a little with increase of power. The measured EEDFs exhibit Druyvesteyn-like distribution at all pressures and powers. Data are analyzed and will be presented.
    Keywords: Plasma Physics
    Type: 53rd Gaseous Electronics Conference; Nov 24, 2000 - Nov 27, 2000; Houston, TX; United States
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