IR SPECTRAL SHIFTS AND ADSORPTION POTENTIALS OF CO AND N-2 ADSORBED ON LIF AND LICL

Following our recent work on IR spectra of molecules adsorbed on C-60 embedded in LiF and LiCl films, adsorption potentials of CO and N-2 ad sorbed on LiF (100) and LiCl (100) were calculated. For CO on LiF, a v alue of 2.0 kcal mol(-1) was obtained, close to that calculated for CO adsorbed of. a single C-60 molecule. The calculated value for CO on L iCl is much higher, 6.8 kcal mol(-1). It is therefore concluded that i n the case of CO adsorbed on mixed LiF/C-60 films, the adsorbed CO mol ecules are distributed almost evenly on the LiF and C60 Single molecul es, whereas in the case of CO adsorbed on mixed LiCl/C-60 films the sa lt is greatly preferred as the adsorption site. Adsorption potential c alculations for a similar system, N-2 on LiF and LiCl, gave values of 1.5 and 4.4 kcal mol(-1), respectively. In this case, a much too large value was found for the adsorption potential on the LiCl surface. IR spectra of CO on the two substrates showed two strong absorptions for each of them. With N-2 induced spectra were obtained. Spectral shifts have been calculated for the above systems and were all toward higher frequencies, in agreement with experimental findings. (C) 1998 Elsevie r Science B.V. All rights reserved.