IR PHOTOMETRY OF THIN FILMS ON SINGLE CRYSTAL DIELECTRIC SUBSTRATES

$^{1}$ H.-C. Chang, H. H. Richardson and E. Ewing, J. Chem. Phys. 89 (1988) 7561. $^{2}$ O. Berg and G. Ewing, Surf. Sci. (submitted).Author Institution: Department of Chemistry, Indiana University; Department of Chemistry, Ohio UniversityWe have developed techniques for measuring high resolution infrared spectra of monolayers of small molecules such as CO or $CO_{2}$ on the (100) faces of single crystals of $NaCl^{1,2}$. The high quality of our data allows the photometry of these systems to be discussed quantitatively. Accordingly, we have developed Maxwell's equations to account for the adsorption of light by these thin films. The measured integrated absorbance for each of these monolayers is compared with the results of simple models which calculate this quantity from isolated gas phase properties. The discrepancy between calculated and measured values differs by 25\% or less. Adsorption of molecules onto NaCl(100) therefore alters their optical properties only slightly