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  • 42.65  (3)
  • 42.65.−k  (1)
  • in situ catalysis  (1)
  • 1
    ISSN: 1572-879X
    Keywords: in situ catalysis ; propylene hydrogenation ; STM ; SFG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sum frequency generation (SFG), using non-linear laser optics, detects vibrational spectra of submonolayer amounts of adsorbates with excellent energy and time resolution. Scanning tunneling spectroscopy (STM) is sensitive to the atomic surface structure; readily imaging defects, steps and kinks as well as stationary adsorbed species. Both of these techniques can be used during reactions at high pressures and temperatures to obtain molecular information in situ. We report studies of propylene hydrogenation over Pt(111) crystal surfaces at atmospheric pressures and 300 K using SFG and STM. Four surface species (2-propyl, π-bonded propylene, di σ-bonded propylene, and propylidyne) were identified; the first two being implicated as reaction intermediates. The platinum surface structure remains unchanged during the reaction, consistent with the structure insensitive nature of olefin hydrogénation. Propylene decomposition induced substantial surface reconstruction.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0649
    Keywords: 42.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 14 (1977), S. 65-77 
    ISSN: 1432-0630
    Keywords: 42.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We have studied experimentally self-focusing of light in the liquid crystalline mediump-ethoxybenzyldine-p-butylaniline (EBBA). By variation of temperature, the response time of the field-induced refractive index was adjusted from larger than to smaller than theQ-switched laser pulsewidth. Accordingly, self-focusing varied from transient to quasi-steady-state. The results agree well with existing theoretical predictions and can be qualitatively understood from a simple physical description. The induced stimulated Brillouin scattering was also measured and was shown to be responsible for the limiting diameter of the self-focused beam in the present case.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 25 (1981), S. 49-56 
    ISSN: 1432-0630
    Keywords: 42.65 ; 78.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Four-wave mixing with two circularly polarized counter-propagating waves inducing a helical birefringence structure can be used to measure a number of material parameters of a liquid crystalline medium. Application to a cholesteric substance is particularly interesting. A resonant effect is expected when the induced helix has a pitch coinciding with the natural helical pitch of the medium towards the isotropic → cholesteric transition. Field-induced shift in the transition temperature is also expected.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 59 (1994), S. 541-543 
    ISSN: 1432-0630
    Keywords: 42.65.−k
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A brief overview on second-harmonic generation and sum-frequency generation as surface analytical tools is given with a discussion on the intrinsic limitations of the techniques often encountered in the applications. The possibly of using nonlinear optical processes for surface studies has attracted increasing attention in recent years. Optical Second-Harmonic Generation (SHG) and Sum-Frequency Generation (SFG), in particular, have been well accepted as viable surface probes [1]. They have many advantages over the conventional techniques. By nature, they are highly surface-specific and has a submonolayer sensitivity. As coherent optical processes, they are capable of in-situ probing of surface in hostile environment as well as applicable to all interfaces accessible by light. With ultrafast pump-laser pulses, they can be employed to study surface-dynamic processes with a subpicosecond time resolution. These advantages have opened the door to many exciting research opportunities in surface science and technology. This paper gives a brief overview of this fast-growing new area of research.
    Type of Medium: Electronic Resource
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