Infrared spectroscopic investigation of the adsorption of fluoromethane on sodiumchloride surfaces under ultra high vacuum

Abstract

The adsorption of CH 3F on NaCl between 77 K and 250 K was investigated using infrared spectroscopy under ultra high vacuum conditions. All internal normal modes of the adsorbate were observed and assigned. Three adsorption phases were detected. The largest frequency shift with respect to the gas takes place for the most intense mode, the C-F stretch ν 3, − 102 cm −1 ( 10 %) for α-CH 3F-NaCl(film) on NaCl(100), while the other modes were much less influenced. No splitting of the vibrations degenerate in the gas occurs. Adsorption isotherms and the isosteric heats of adsorption were determined.