PNNL

Abstract

Obtaining the complex refractive index vectors n(? ~ ) and k(? ~ ) allows calculation of the (infrared) reflectance spectrum that is obtained from a solid in any of its many morphological forms. We report an adaptation to the KBr pellet technique using two gravimetric dilutions to derive quantitative n(? ~ )/k(? ~ ) for dozens of powders. The optical constants of bisphenol A and sucrose are compared to those derived by other methods, particularly for powdered materials. The variability of the k values for bisphenol A was examined by ten individual measurements, showing an average coefficient of variation for k peak heights of 5.6%. Limitations and advantages of the method are discussed, the salient advantage being a method to drive n/k for those species that do not readily form crystals or specular pellets.