Spectroscopy making use of the properties of chiral substances when they interact with polarized light of various wavelengths. Optical rotatory dispersion (the change of optical rotation with wavelength) and circular dichroism are old examples of chirooptical spectroscopy. More recent types of chirooptical spectroscopy are vibrational optical rotatory dispersion, vibrational circular dichroism. (VCD), and Raman optical activity (ROA), which are all the result of the interaction between chiral substances and polarized infrared electromagnetic radiation; these techniques are known as vibrational optical activity (VOA), as they are associated with transitions in the vibrational energy levels in the electronic ground state of a molecule. Chirooptical spectroscopy is used in the analysis of the structure of molecules.