Picosecond pump-probe study of adsorbed hydroxyl group

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The population lifetimes of the OH stretching mode of a water molecule hydrogen-bonded to the Bronsted acidic hydroxyl group in a mordenite-type zeolite have been measured at various temperatures using an infrared picosecond pump-probe technique. An extraordinary temperature dependence has been observed for the lifetime of hydrogen-bonded H2O,which was explained by the creation of one quantum of the adbond vibrational mode and two bulk phonons in the relaxation process.Transient absorption spectra were observed on vibrationally exciting the OD group of a water molecule (D2O) adsorbed on a acidic hydroxyl group of a zeolite. A transient absorption signal was assigned to the combination band due to the intra-molecular vibrational redistribution. The lifetime of the newly appeared band was determined to be shorter than 15 ps.