The measured 10 μm refractive index of some simple molecules (CO, H 2O, CH 4, C 2H 2) and their calculated extension to the whole IR frequency region

Abstract

The refractive index of some simple molecules has been determined with different CO 2 laser lines in the 10 μm region. Some gases show a frequency dependence of the refractive index. This frequency behaviour can be related in a simple way to the presence of an absorption band adjacent to the 10 μm region. This simple relation allows to derive with good accuracy the integrated absorption intensity S ν 0 of the involved bands. In this way the model validity is confirmed and the model can be used to calculate the theoretical refractivity over the whole IR region (<5000 cm −1) by using the S ν 0 values of all the IR bands reported in literature.