IR spectra of CO adsorbed on mixed films of [formula omitted] and [formula omitted]

Abstract

In the present work, IR spectra of CO adsorbed on mixed alkali halide C 60 high surface-area films were investigated. The mixed films were prepared either by simultaneous or by subsequent operation of two evaporation sources and condensing the vapors on a CsBr window cooled to 77 K. The IR spectrum of CO adsorbed on LiF C 60 films prepared by simultaneous deposition showed three absorptions of comparable intensities at 2175, 2162-2153 (depending on coverage) and 2130 cm −1. The first two bands are identical to absorption of CO on pure LiF. The band at 2130 cm −1 is assigned to CO on single C 60 molecules dispersed in the LiF. With LiF C 60 films prepared by subsequent deposition of the two substrates, four bands appeared in the spectrum, at frequencies closely resembling the frequencies obtained with CO adsorbed on the separate films. With mixed NaCl C 60 films absorption bands due only to CO on NaCl were seen. No absorptions were seen for CO on C 60 except at high surface coverages, where a very faint band at 2130 cm −1 appeared. Spectroscopic measurements of the isosteric heats of adsorption of CO on C 60 and LiF and adsorption potential calculations were performed.