Investigations at the air/water interface using polarization modulation IR spectroscopy

The ability of polarization modulation IR reflection absorption spectroscopy (PM-IRRAS) to study the air/water interface is presented. A brief description of the set-up and of the experimental procedure is given. Theoretical simulations accounting for the uniaxial nature of the spread monolayer lead to optimum experimental conditions (71 degrees for the angle of incidence) and to a specific surface selection rule. Application to the study of cadmium arachidate, dimyristolyl phosphatidylcholine (DMPC) and polypeptidic Langmuir films illustrates the potential uses of this method.