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30 December 1998 Surface studies using nonlinear spectroscopy with tunable picosecond pulses
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Chemisorbed films of octadecyltrichlorosilane (OTS) and ethyltrichlorosilane (ETS) at the interface calcium fluoriderair have been studied by vibrationally resonant IR pump IR-vis probe sum-frequency (SF) spectroscopy. Using a total internal reflection geometry, a signal enhancement of more than two orders of magnitude compared to the conventional setup is achieved. This enhancement in combination with two independently continuously tunable in- dielectric surfaces. A fast energy exchange between the CH3-stretching modes detected by SF spectroscopy occurs within a few picoseconds. A two-exponential decay of the CH3-stretching modes is observed: the energy relaxation is fast with time constants in the picosecond range, while the ground sate is repopulated in approximately 100ps. of a SF-active mode can be achieved, even if the pumped mode does not directly contribute to the SF spectrum. This weakening of the selection rules in IR pump IR-vis probe SF spectroscopy is demonstrated for the methylene stretching vibrations of OTS.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
J. Loebau and Alfred Laubereau "Surface studies using nonlinear spectroscopy with tunable picosecond pulses", Proc. SPIE 3683, Laser Optics '98: Superstrong Laser Fields and Applications, (30 December 1998);

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