The surprisingly short vibrational lifetime of the internal stretch of CO adsorbed on Si(100)

Picosecond sum-frequency generation spectroscopy has been employed to study the dynamics of the internal stretch vibration of CO adsorbed on a Si(100) surface. Using the IR pump-sum-frequency generation probe method, the vibrational lifetime of the C-O stretch vibration has been determined to be 2.3+/-0.5 ns. Within the experimental error limits, the identical lifetime was observed for 12C16O and 13C16O. No strong dependency on the carrier density in the substrate, inferred from measurements using differently doped crystals, was observed.