SYNCHROTRON INFRARED-SPECTROSCOPY OF H2O ADSORBED ON POLYCRYSTALLINE GOLD

Synchrotron infrared spectra of H2O adsorbed on a polycrystalline gold surface have been obtained for the first time. Water was found to adsorb molecularly and associatively on gold at low temperatures, i.e., 100-140 K. For example, at 117 K and exposure of 0.3 langmuirs, the O-H stretching vibration was observed at 3387 cm-1, which is indicative of hydrogen-bonded surface water. Bands attributed to frustrated translation were observed at about 230 and 290 cm-1; a band at 817 cm-1 was assigned to frustrated rotational motion. The assignments were confirmed through isotopic shift measurements with D2O. The observed spectra are suggestive of the formation of (HOH)n clusters at low coverage; with increasing coverage, the formation of an ordered multilayer with an icelike structure is apparent.