Time-resolved measurements of vibrational relaxation of molecules on surfaces: Hydroxyl groups on silica surfaces

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Abstract
The vibrational population relaxation rate of the O–H stretching fundamental of hydroxyl groups on SiO2 surfaces was measured directly using picosecond infrared pulses. The vibrational lifetime determined for hydroxyls at the silica–vacuum interface is 204±20 ps. For silica-bound hydroxyls in a saturated atmosphere of CCl4, the lifetime decreases to 159±16 ps. Both lifetimes are many times longer than would be inferred from infrared absorption linewidths.