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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 1730-1739 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper we present a study of the vibrational energy relaxation processes of chloroform, bromoform, and iodoform in solution after excitation of the C–H stretch vibration. The relaxation is studied with ultrafast infrared saturation spectroscopy using intense infrared pulses with a pulse duration of 19 ps. The experiments were performed in a polar and a nonpolar solvent in order to study the effects of the polarity of the solvent on the relaxation processes. We observe that in both types of solvent the relaxation takes place via two consecutive relaxation processes and that the relaxation leads to ultrafast changes of the absorption band of the C–H stretch vibrations. We discuss the differences in the time constants of the relaxation processes of the haloforms in terms of the energy differences between the vibrational levels and the interactions with the solvent.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 6007-6013 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper we present a time-resolved study of the vibrational relaxation after excitation of the asymmetric CH2 stretch vibration of dibromomethane and diiodomethane and the C–H stretch vibration of 1,1,2,2-tetrabromoethane. The experiments were performed in a polar and a nonpolar solvent in order to study the influence of the polarity of the solvent on the relaxation. We observe that in both types of solvent the vibrational energy transfer is successively intra- and intermolecular and that the intramolecular relaxation leads to a shift of the transition frequency of the excited molecular vibration. We discuss the experimentally determined time constants of the relaxation in terms of the energy differences between the molecular vibrations and the interactions with the solvent.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 1715-1719 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have built a relatively simple, highly efficient, THz emission and detection system centered around a 15 fs Ti:sapphire laser. In the system, 200 mW of laser power is focused to a 120 μm diam spot between two silverpaint electrodes on the surface of a semi-insulating GaAs crystal, kept at a temperature near 300 K, biased with a 50 kHz, ±400 V square wave. Using rapid delay scanning and lock-in detection at 50 kHz, we obtain probe laser quantum-noise limited signals using a standard electro-optic detection scheme with a 1-mm-thick (110) oriented ZnTe crystal or a (110) oriented 0.1-mm-thick GaP crystal. The maximum THz-induced differential signal that we observe is ΔI/I=7×10−3, corresponding to a THz peak amplitude of 95 V/cm. The THz average power was measured to be about 40 μW, to our knowledge, the highest power reported so far generated with Ti:sapphire oscillators as a pump source. The system uses off-the-shelf electronics and requires no microfabrication techniques. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 2213-2215 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We create forced excitonic charge oscillations in semiconductor heterostructures by excitation with periodic optical pulse sequences. The far-infrared radiation that accompanies the charge oscillations shows temporal interference patterns for pulse sequences with different optical phase profiles, providing evidence for phase induced population transfers between exciton levels in a semiconductor.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 347 (1990), S. 745-747 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In our experiment, a significant fraction of the molecules is directly vibrationally excited with an intense infrared pulse (pump). These excited molecules can no longer absorb infrared light of the same frequency and therefore the sample will be more transparent as long as the excited molecules ...
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-0649
    Keywords: 71.35.+z ; 42.50.Md ; 42.65.Re ; 84.40.-x
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The observation of terahertz electromagnetic dipole radiation from quantum well structures has finally proven the existence of charge oscillations in semiconductors associated with wave packet dynamics. This article closely examines the physics behind the emission of terahertz electromagnetic radiation from excitonic charge oscillations in such quantum well structures, points out similarities and differences between the various generation schemes, and discusses the various relaxation mechanisms involved. Finally, we show how both amplitude and phase of charge oscillations and the corresponding terahertz emission can be manipulated using phase-locked optical pulses.
    Type of Medium: Electronic Resource
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