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  • 1
    Electronic Resource
    Electronic Resource
    Magnetic measurements on the TCV Tokamak (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2333-2348 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The TCV Tokamak was designed to create a large variety of plasma shapes. Such a large flexibility requires high precision magnetic measurements with a good spatial coverage. This article gives a detailed description of the magnetic sensor geometry, fabrication, calibration, the associated electronics, and the diagnostic operation and monitoring. A substantial effort has been made to quantify the precision in the measurements and a novel method has been developed to derive corrections in the sensor position and calibration which optimise the consistency of the entire measurement set. Accuracy of 0.5 mWb in the poloidal flux and 1 mT in the magnetic field with a position error of a few mm have been achieved. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148940
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  • 2
    Electronic Resource
    Electronic Resource
    Helium atom scattering from isolated CO molecules on copper(001) (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 2093-2098 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Angular distributions have been measured for helium atoms scattering from isolated CO molecules chemisorbed on a Cu(001) surface as a function of incident beam energy between 9.4 and 100 meV and surface coverage from 1.3% ML to 9.3% ML. Up to five oscillations are clearly observed in the angular distributions. The parallel wave vector transfers of the peaks vary only slightly with incident energy and are independent of coverage up to 20% of a c(2×2) layer. New hard wall scattering calculations show that all of the distinct peaks observed can be explained by interference structures involving both Fraunhofer diffraction and illuminated face scattering from CO molecules with an approximate hard wall radius of 2.4 A(ring) with no evidence of the classical rainbows predicted in several recent theoretical studies. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472075
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  • 3
    Electronic Resource
    Electronic Resource
    Quasielastic helium atom scattering measurements of microscopic diffusion of CO on the Ni(110) surface (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 11297-11304 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The microscopic diffusion of CO on the Ni(110) surface has been studied by quasielastic helium atom scattering. From the temperature dependence of the energetic broadening of the quasielastic peak measured at a parallel wave vector near the Brillouin zone boundary, the activation energies for diffusion have been determined to be Ediff=57±4 and 35±4 meV for diffusion parallel to the rows (〈11¯0〉) and perpendicular to the rows (〈001〉), respectively. The activation energies are a factor 2–6 smaller and the preexponential diffusion coefficients orders of magnitude larger than obtained in recent laser measurements of chemical diffusion coefficients, indicating that diffusion over distances from about a few A(ring)ngstroms up to 30 A(ring) is much faster than over the much larger distances probed in macroscopic diffusion measurements. The difference is attributed to the impeding effect of step edges or impurities on the latter measurements. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472983
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  • 4
    Electronic Resource
    Electronic Resource
    A helium atom scattering study of the growth and dynamics of CH4 and C2H6 on Cu(001) (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 2502-2512 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The growth, structure and dynamics of methane and ethane monolayers on Cu(001) have been studied using high resolution helium atom scattering. Specular intensity measurements of the growth behavior reveal an island growth mode for methane and ethane, indicative of an attractive interatomic interaction. Diffraction measurements show that the methane monolayer forms a hexagonal structure, incommensurate in one direction, with a lattice constant of 4.18 Å, while ethane forms a structure with an interatomic distance of 5.10 Å. The frustrated translational vibrations perpendicular to the surface (S mode) of methane and ethane have been measured with inelastic helium scattering and have frequencies of 6.5 meV and 6.8 meV, respectively. In addition, the desorption energies were determined to be 165 meV for methane and 260 meV for ethane, in both cases independent of coverage. These results are compared with recent measurements made for C2H4 and larger alkanes adsorbed on Cu(001). © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473156
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  • 5
    Electronic Resource
    Electronic Resource
    Experimental determination of a longitudinal phonon dispersion curve in a quasi-two-dimensional system (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 6194-6197 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The structural and dynamical properties of a monolayer of Xe atoms adsorbed on a Cu(001) surface have been studied with high-resolution He-atom scattering. Angular distributions reveal a phase-transition from the high-temperature in commensurate phase to a new, more densely packed, phase upon cooling below 65 K. For both phases the strongly dispersive longitudinal phonon mode could be detected. A lattice-dynamical analysis yields a substrate mediated softening of the Xe–Xe radial force constant down to 25% of that obtained from gas-phase potentials and a fit of Xe bulk phonon data. This decrease is much larger than assumed in previous work for noble gas atoms adsorbed on metals. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473242
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  • 6
    Electronic Resource
    Electronic Resource
    The transition from single phonon to multiphonon energy transfer in atom–surface collisions (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 1234-1247 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The angular distributions and time-of-flight spectra of nearly monoenergetic He atoms with incident energies of 82 meV and 112 meV have been measured after scattering from a clean Cu(001) surface over a large range of crystal temperatures from 100 K to 1000 K. With increasing temperatures the sharp diffraction and phonon peaks of the low temperature quantum regime become broad and featureless as expected for the multiphonon classical regime. The results are compared with a quantum mechanical theory which is able to explain the height, position, width, and area under the multiphonon maximum. In the classical regime, the temperature dependence of the inelastic intensity indicates that the He atoms are reflected by a smooth vibrating barrier presumably due to the surface electron density, and not by a lattice of discrete repulsive surface atomic cores. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473220
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  • 7
    Electronic Resource
    Electronic Resource
    Response to "Comment on ‘Experimental determination of a longitudinal phonon dispersion curve in a quasi-two-dimensional system' " [J. Chem. Phys. 107, 4443 (1997)] (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 4445-4445 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474806
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  • 8
    Electronic Resource
    Electronic Resource
    Molecular diversity of cyclic nucleotide-gated cation channels (1995)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 353 (1995), S. 1-10 
    Details
    ISSN: 1432-1912
    Keywords: Key words Cyclic nucleotide-gated channels ; Second messenger ; Cyclic GMP ; Calcium ; Nitric oxide ; Molecular cloning ; Gene family
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Cyclic nucleotide-gated cation channels (CNG channels) form a multi-gene family consisting of at least five distinct members (CNG1–5). Expression studies have indicated that only CNG1–3 are able to form functional homooligomeric channels. Although structurally related, the cDNAs of CNG4–5 fail to induce cyclic nucleotide-dependent currents when expressed alone. However, when co-expressed with CNG1–3 they confer some of the physiologically observed properties of native CNG channels which are absent from the homooligomeric CNG1–3 channels. CNG channels are expressed in several tissues and cell types pointing to a general function of these channels in a wide variety of cellular systems. There is now increasing evidence that a major function of CNG channels may consist in providing a second messenger-regulated pathway for Ca2+ influx.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00168909
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  • 9
    Electronic Resource
    Electronic Resource
    The low-energy thermal excitation spectrum of nitrogen molecules adsorbed on Ni(110): Implications for molecular adsorption sites (1996)
    Springer
    Applied physics 62 (1996), S. 95-101 
    Details
    ISSN: 1432-0630
    Keywords: 34.50 ; 79.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01575707
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  • 10
    Electronic Resource
    Electronic Resource
    The low-energy thermal excitation spectrum of nitrogen molecules adsorbed on Ni(1 1 0): Implications for molecular adsorption sites (1996)
    Springer
    Applied physics 62 (1996), S. 95-101 
    Details
    ISSN: 1432-0630
    Keywords: PACS:  34.50; 79.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract.  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 ν1 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003390050272
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