Measurement of the absorption spectrum of polytetrafluoroethylene in the near millimetre region by an untuned cavity

The absorption spectrum of polytetrafluoroethylene has been measured between 3 and 15 cm −1, a region which until now has been virtually unexplored. Absorption was found to arise almost entirely from amorphous regions of the sample and absorption in crystalline regions is small. A novel feature of the investigation is that measurements are made in an untuned cavity which has the advantage for low loss materials, that losses from reflection, scatter, and diffraction become unimportant. Loss measurements can be made on samples even when they are in the form of fine powder.