4. Gas transmission

All volatile organic compounds have specific absorption lines that depend on the structure of the molecule. For example, the $\text{C}—\text{H}$ bond has an absorption line at around 3.4 µm, so this line will be present in the spectrum of all hydrocarbons. In IR band III (8 to 14 µm), absorption lines are a particular signature of the molecule. As examples, we present the absorption spectrum of methane CH ₄ (figure 4 ) and that of benzene C ₆ H ₆ (figure 5...