Time Resolved Measurements of Vibrational Relaxation of Molecules on Surfaces: Hydroxyl Groups on Silica

摘要

The vibrational population relaxation rate of the O-H stretching fundamental of hydroxyl groups on Si02 surfaces was measured directly using picosecond infrared pulses. The vibrational lifetime determined for hydroxyls at the silica-vacuum interface is 204 + or - 20 ps. For silica-bound hydroxyls in a saturated atmosphere of CC14, the lifetime decreases to 159 + or - 16 ps. Both lifetimes are many times longer than would be inferred from infrared absorption linewidths.