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O: Oberflächenphysik
O 5: Zeitaufgelöste Spektroskopie I
O 5.7: Vortrag
Freitag, 4. März 2005, 12:15–12:30, TU EB107
Vibrational dynamics of the C-O stretching mode of CO:Si(100) — •Kristian Laß, Xu Han, and Eckart Hasselbrink — Fachbereich Chemie, Physikalische Chemie, Universität Duisburg-Essen, Standort Essen, Universitätsstr. 5, D-45141 Essen
Surface infrared-visible sum frequency generation (SFG) spectroscopy (using ps laser pulses) has been utilised to study the vibrational dynamics of the internal stretching mode of CO molecularly adsorbed on a Si(100) surface. The structure of the CO-adsorbed Si(100) surface is not known in detail; however, two slightly different adsorbed species have been suggested in the past. With our IR laser linewidth of 9 cm−1, only one resonance was distinguishable, whose linewidth was significantly lower than our laser linewidth. Using a IR-pump-SFG-probe setup, the vibrational lifetime of the system could be determined to be about 2 ns. This value is unexpectedly short, in view of the fact that the vibrational excitation cannot couple to electron-hole pairs because of the large bandgap in Si. The lifetime appears to be independent of the carrier density of the Si crystal (within the accuracy of our experiment), as judged from the vibrational lifetime measured on crystals with different dopant densities.