IR spectral shifts and adsorption potentials of CO and N2 adsorbed on LiF and LiCl

Abstract

Abstract 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 adsorbed on LiF (100) and LiCl (100) were calculated. For CO on LiF, a value of 2.0 kcal mol −1 was obtained, close to that calculated for CO adsorbed on a single C 60 molecule. The calculated value for CO on LiCl is much higher, 6.8 kcal mol −1 . It is therefore concluded that in the case of CO adsorbed on mixed LiF/C 60 films, the adsorbed CO molecules are distributed almost evenly on the LiF and C 60 single molecules, whereas in the case of CO adsorbed on mixed LiCl/C 60 films the salt is greatly preferred as the adsorption site. Adsorption potential calculations 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.