Infrared reflection-absorption spectroscopic study on the adsorption structures of acrylonitrile on Ag(111) and Ag(110) surfaces

Infrared reflection-absorption spectra in CN stretching, CH(2) out-of-plane wagging and CH(2) twisting vibration regions were measured for acrylonitrile (CH(2)-CHCN) exposed to Ag(111) and Ag(110) in increasing amounts at 77 K. The adsorbate on Ag(lll) takes on a series of discrete adsorption states; i.e., an isolated state, associated states, and ordered and amorphous multilayer states. The adsorbate on Ag(110) at lower exposures is in a state with the CN group weakly coordinated to a silver atom (or silver atoms). The adsorbate on Ag(110) takes the associated state and the amorphous multilayer at larger exposures. On raising the temperature to 96 K, the amorphous states on both Ag(lll) and Ag(110) are converted to the ordered multilayer. The desorption temperature of the ordered multilayer is below 99 K for Ag(110), while the temperature is above 107 K for Ag(lll); the result indicates the effect of the surface morphology on the stability of the ordered state. (C) 1999 Elsevier Science B.V. All rights reserved.