Analysis of infrared emission from thin adsorbates

Fuel and lubricant deposits on solid surfaces, though often of similar visual appearance, differ in composition, depending on the nature of the deposit formers and the circumstances of deposition. To help establish these relations an Infrared Emission Fourier Polarization Microspectrophotometer was constructed to record infrared spectra from the deposits on their original support. By focussing on small aggregates with a reflecting microscope objective and by discriminating against the randomly polarized blackbody radiation with a rotating polarizing filter phase-locked to an amplifier, excellent Fourier emission spectra of polarized bands could be obtained. In many instances, the microscope objective was adequate without the polarizer. The analysis was calibrated against a very thin film of polyethylene terephthalate attached to a highly reflective aluminum mirror on the sample positioner.