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  • 1
    Electronic Resource
    Electronic Resource
    Collisional effects on spectral line shape from the Doppler to the collisional regime: A rigorous test of a unified model (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 158-166 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The paper presents high resolution Raman investigations of the Q(1) line of H2 in Ar mixture from low density (Doppler regime) to high density (collisional regime) analyzed with a unique line shape profile. Measurements are performed by stimulated Raman gain spectroscopy between 300 and 1000 K in a wide density range (from 0.2 to 11 amagat). All the observed spectral features are accurately described by a unified model recently proposed by two of the authors. This model accounts for a velocity-memory process, not restricted to the usual hard and soft limits. It also includes correlation between velocity- and phase-changing collisions. An exhaustive analysis of various possible mechanisms on the line shape is achieved. These mechanisms are the Dicke narrowing, the radiator speed dependence of the collisional broadening and shifting parameters, the collisionally induced speed-class exchange and the nonimpact effect. The present test shows the high consistency of the unified model, since it allows one to get a remarkable agreement with all the data by using a unique set of parameters. This model should be useful for optical diagnostics at moderate density, as required for combusting media or atmospheric work. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480570
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  • 2
    Electronic Resource
    Electronic Resource
    Investigations of pure rotational transitions of H2 self-perturbed and perturbed by He. I. Measurement, modeling, and quantum calculations (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 951-961 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High resolution stimulated gain Raman spectroscopy is used to investigate the collisional parameters of pure rotational S0(j=0–4) lines of H2 in pure H2 and H2–He mixture. Measurements are performed between 300 and 1000 K in a density regime where the lines are essentially collisionally broadened (typically 10 amagat). For the first time, these highly accurate measurements of the frequencies of pure rotational lines allow one to correct previously measured values that did not take into account the collisional frequency shift. For both collisional systems, the shifting coefficients exhibit a linear behavior with the square root of temperature, similar to the behavior already observed in the Q branch. The broadening coefficients of the S0 branch increase nonlinearly with temperature contrary to the Q branch. For the H2–He system, both these new S0(j) data and previously measured Q(j) data are analyzed using a modeling of the broadening coefficients in terms of elastic and inelastic contributions. These different contributions are analyzed as a function of temperature and of the rotational quantum number j. Preliminary quantum calculations are used to assess the validity of the model. Further calculations will be presented in paper II. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.476638
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  • 3
    Electronic Resource
    Electronic Resource
    Ultrafast optical switching of second-harmonic generation at the C60 single-crystal surface (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3781-3783 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The switching of second-harmonic generation (SHG) at a C60 single-crystal surface has been observed in a pump-and-probe experiment. The SHG signal from a picosecond 1.17 eV laser pulse is suppressed by one order of magnitude upon illuminating the crystal surface with a 3.49 eV pump pulse. The nonlinear optical response is faster than 45 ps and persists for longer than 20 ns. SHG suppression to 1/e occurs at pump densities as low as 2.8 μJ/cm2. We suggest that nonlocalized excited electronic states determine the change in the nonlinear optical behavior. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361213
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  • 4
    Electronic Resource
    Electronic Resource
    Spatially localized energy shifts in the photoemission spectroscopy of insulators (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 3710-3713 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Core-level photoemission peaks taken on several insulators with spatial resolution of 30–300 μm rigidly shift in energy from place to place, most likely because of local charging effects. Such phenomena can affect the linewidth and the general lineshape of conventional, spatially integrated spectra even when a flood gun is used, which is one of the standard remedies against charging. This may require a critical revision of photoemission linewidths and lineshapes for many past experiments on insulators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357440
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  • 5
    Electronic Resource
    Electronic Resource
    Electronic structure of anatase TiO2 oxide (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 2945-2951 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoemission spectromicroscopy was used to investigate the electronic structure of TiO2 anatase single crystals and polycrystalline thin films. The stoichiometry and the degree of oxidation of as-grown crystals, as-deposited films, as well as of thermally annealed samples in different atmospheres, were analyzed, based on the Ti 2p and O 1s core levels, with an energy resolution of 0.4 eV. The experimental density of states (DOS) was found to be in agreement with the theoretical DOS reported in the literature for anatase crystals, and shows some characteristics similar to the experimental DOS reported for rutile crystals. In reduced samples, the experimental DOS is characterized by intense emission in the region of O 2p bonding orbitals, and does not exhibit an appreciable density of states in the band gap. As-grown crystals exhibit small band gap emission (a few percent of the valence band VB signal) at about 0.8 eV, which is attributed to Ti3+ (3d) defect states. Annealing the crystals at high temperatures in O2 or subsequent thermal reduction in an Ar–H2 mixture (95%–5%) produces nearly stoichiometric surfaces with smaller or undetectable density of Ti3+ states. In addition, some redistribution of the spectral weight is observed in the VB spectra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356190
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  • 6
    Electronic Resource
    Electronic Resource
    Speed-dependent line profile: A test of a unified model from the Doppler to the collisional regime for molecule–molecule collisions (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 4951-4956 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A speed-dependent line profile combining soft and hard fully correlated Dicke-narrowing collisions was recently successfully tested on Ar-broadened H2 spectra in a wide density and temperature range. A further test for mixtures of H2 in nitrogen molecules (instead of Ar atoms) is presented. This test is also based on high resolution Raman investigation of the isotropic Q(1) line of H2 from low to high density at various temperatures. The same consistency of the speed-dependent line profile as for H2–Ar is obtained for H2–N2 through a remarkable agreement with all the data by using a unique set of four parameters (the collisional width and shift, the kinetic frequency, and a characteristic velocity memory parameter). The present study is a preliminary step for the hydrogen CARS thermometry in H2–air flames at high pressure. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1287824
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  • 7
    Electronic Resource
    Electronic Resource
    Environmentally compatible surfactants for the cosmetic industry (1997)
    Oxford, UK : Chapman and Hall
    International journal of cosmetic science 19 (1997), S. 0 
    Details
    ISSN: 1468-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: From the application pattern of surfactant-containing cosmetic products, it is inevitable that the major part of the chemicals will be discharged into waste water and eventually will enter the environment. Because the environmental compatibility of the products is based on the ecological properties of their raw meterials, the biodegradability and ecotoxicological behaviour of the product components and particularly the surfactants, form the central elements of the environmental compatibility assessment. The tools for this evaluation are standardized test systems, which are described and discussed on the basis of the ecological data of selected surfactants. De par le type d'application des produits cosmetiques contenant des tensioactifs, il est inevitable que la plus grande partie des substances chimiques soit evacuee dans les eaux usees et finisse par arriver dans l'environnement. Puisque la compatibilite environnementale des produits est basee sur les proprietes ecologiques de leurs matieres premieres, la biodegradabilite et le comportement ecotoxicologique des composants des produits, et en particulier des tensioactifs, forment les elements majeurs de l'evaluation de la compatibilite environnementale. Les outils de cette evaluation sont des systemes d'essai normalises, qui sont decrits et commentes d'apres les donnees ecologiques de tensioactifs choisis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1467-2494.1997.tb00186.x
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  • 8
    Electronic Resource
    Electronic Resource
    Raman studies of the growth mechanism of ZnSe/GaAs(001) heterostructures (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3916-3920 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Monocrystalline ZnSe/GaAs(001) heterostructures have been grown by atomic layer epitaxy with typical thicknesses up to 200 nm. The 1LO Raman spectrum of ZnSe and GaAs, respectively, was recorded in situ during growth interruptions. The spectra were analyzed with respect to Raman intensity, phonon frequency, and bandwidth. Two different growth modes are distinguishable: (i) The biaxial compressive strain in the epilayers is increased in the thickness range up to 40 nm due to lattice mismatch of the heterosystem. This can be interpreted as a transition from an initial 3D island to the 2D layer by layer growth. (ii) When larger thicknesses (40–170 nm) are reached the strain is constant and the 1LO Raman intensity from the epilayer and from the substrate oscillates significantly with thickness. These periodic oscillations are quantitatively described in the framework of interference-enhanced Raman scattering and verify the 2D growth mode in this thickness range. The crystalline quality and the final thickness of the samples were determined by transmission electron microscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354490
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  • 9
    Electronic Resource
    Electronic Resource
    VOLATILIZATION OF PLATINUM. (1904)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 26 (1904), S. 1512-1515 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja02001a012
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  • 10
    Electronic Resource
    Electronic Resource
    Inhomogeneous and thickness-dependent chemical reactivity at GaSe–Si interfaces (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 7694-7696 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Scanning photoelectron spectromicroscopy experiments on the edge of patterned Si overlayers on GaSe revealed the presence of an inhomogeneous reaction with a metallic-like Ga phase separation. The Si–Se chemically shifted components show lateral variations and a thickness-related SiSe2/SiSex (x=0.5, 1, and 1.5) ratio on a micrometer scale. The dependence of the peak intensities on the overlayer thickness suggests an initial layer-by-layer coverage until (approximate)2 Å, followed by a clustering growth mode. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370573
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