The molecular vibrations of many chemical COMPOUNDS can be excited by energies that lie in the infrared wavelength range. THEREFORE, these substances absorb infrared radiation. The absorption spectrum depends mainly on the structure of the molecule and thus the degrees of freedom for the movement of the molecular components, their mass, their compositions, their spacing and their binding forces. Therefore, each substance has a characteristic absorption spectrum. For example, in carbon dioxide molecules can be excited bending and stretching vibrations. Additionally rotational movements around different molecular axes are POSSIBLE, which superpose the vibrational spectrum and generate their fine STRUCTURES.

The molecular vibrations of many chemical compounds can be excited by energies that lie in the infrared wavelength range. Therefore, these substances absorb infrared radiation. The absorption spectrum depends mainly on the structure of the molecule and thus the degrees of freedom for the movement of the molecular components, their mass, their compositions, their spacing and their binding forces. Therefore, each substance has a characteristic absorption spectrum. For example, in carbon dioxide molecules can be excited bending and stretching vibrations. Additionally rotational movements around different molecular axes are possible, which superpose the vibrational spectrum and generate their fine structures.