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  • 1
    Electronic Resource
    Electronic Resource
    Formation of amorphous carbon on melting of microcrystalline graphite by picosecond laser pulses (1997)
    Springer
    JETP letters 66 (1997), S. 699-703 
    Details
    ISSN: 1090-6487
    Keywords: 81.05.Gc ; 81.05.Tp ; 64.70.Dv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Observations of microcrystalline graphite subjected to picosecond laser pulses reveal the formation of a liquid phase with a subsequent transition to a uniform amorphous state of a surface layer upon solidification. This phenomenon is observed on a definite type of graphite and with the radiation incident on a plane parallel to the sixfold symmetry axis, and only for certain parameters of the laser pulse. A structural analysis of the amorphous phase is performed by electron microscopy and Raman scattering spectroscopy. A periodic structure with a period of the order of the wavelength of the heating pulse is formed in the heating region. The “rulings” of this periodic structure are oriented in the direction of polarization of the heating pulse. A study of the reflection kinetics of the probe laser pulse showed that the characteristic existence time of the liquid phase and of the solidification process is ∼10−10 s.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.567582
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Formation of periodic surface structures by ultrashort laser pulses (1999)
    Springer
    Journal of experimental and theoretical physics 88 (1999), S. 370-376 
    Details
    ISSN: 1090-6509
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The formation of periodic surface structures by ultrashort laser pulses was observed experimentally and explained theoretically. The experiments were performed on graphite with picosecond laser pulses. The spatial period of the structures is of the order of the wavelength of the incident radiation, and the orientation of the structures is correlated with the direction of polarization of the light. The key point of the theoretical model proposed is resonance excitation of surface electromagnetic waves, which under conditions such that the temperature of the electronic subsystem is decoupled from the temperature of the crystal lattice causes a “temperature grating” to be written on the flat solid surface of the sample while the laser pulse is being applied on account of the temperature dependence of the surface impedance. The formation of a periodic surface profile from the temperature grating occurs by the volume expansion of a melted layer near the surface of the material. For typical values of the surface tension and viscosity for metals, there is not enough time for the periodic profile to be resorbed before the liquid layer solidifies. The formation of periodic surface structures is delayed in time relative to the laser pulse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.558805
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Optical anisotropy as a technique for studying ultrafast phase transformations at solid surfaces (1998)
    Springer
    Journal of experimental and theoretical physics 86 (1998), S. 1184-1190 
    Details
    ISSN: 1090-6509
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new technique for testing long-range order in high-absorption anisotropic crystals has been developed using conversion of an incident p-(s-)wave to an s-(p-)wave due to optical anisotropy. The technique yields time-resolved measurements of parameters related to phase transformations in thin (10−6–10−5 cm) layers with a high resolution (10−12 s). Using picosecond laser pulses and an “Agat” streak camera, the technique has been applied to an experimental investigation of melting and recrystallization kinetics at zinc and graphite surfaces. It was found that the process of melting takes less than 3 ps and the recrystallization time is about 100 ps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.558589
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    Paper (German National Licenses)
    Fulltext
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