The proposed course is designated for the 6th year students (11th semester) and undergraduates, but could be recommended as well for the junior students specialized on the subject and familiar with basics of the course “Physical chemistry of heterogeneous systems”. It shows the actual state of studies of the microstructure of solid surfaces and adsorbed layers by means of optical spectroscopy, mainly IR absorption spectroscopy, widely used nowadays. Taking adsorbed molecules as an example, it teaches to apply spectroscopy for certain problems of physics and chemistry, such as qualitative and quantitative spectral analysis, establishing the structure of compounds and reaction mechanisms, or the nature of intermolecular interactions.