Spectroscopic small loss measurements on infrared transparent materials

Small losses of NaCl, KBr, TICI, KRS-5, CsI, and PbI(2) near 10 microm were measured using an improved differential infrared spectrophotometer with an accuracy better than 0.1% in transmittance. TlCl shows relatively large intrinsic multiphonon absorption, whereas the others show only impurity loss. PbI(2), with the possibility of glass formation, shows its infrared absorption proportional to exp(-omega/37.5), where omega is the frequency in cm(-1).