IR-SPECTRA OF CO ADSORBED ON MIXED FILMS OF LIF C-60 AND NACL/C-60/

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 p repared either by simultaneous or by subsequent operation of two evapo ration 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 simul taneous 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 2 130 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 close ly resembling the frequencies obtained with CO adsorbed on the separat e 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 hig h surface coverages, where a very faint band al 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.