The advent of diffuse reflectance (DR) infrared spectroscopy as a routine technique has greatly facilitated the study of otherwise intractable samples. In particular, studies requiring in situ investigation such as oxidation of coals, carbon, adsorption-desorption processes in catalysts, and other surface-active compounds are being studied by DR.
P. W. Yang and H. L. Casal, "In Situ Monitoring of Solid-State Photochemical Reactions by Diffuse Reflectance Infrared Spectroscopy," Appl. Spectrosc. 40, 1070-1073 (1986)