Single photons in the infrared spectral range usually are not energetic enough for direct photodissociation of molecules. However, after absorption of multiple infrared photons a molecule may gain internal energy to overcome its barrier for dissociation. Multiple-photon dissociation (MPD; IRMPD with infrared radiation) can be achieved by applying high-power lasers, e.g. a carbon dioxide laser, or a free-electron laser, or by long interaction times of the molecule with the radiation field without the possibility for rapid cooling, e.g. by collisions. The latter method allows even for MPD induced by black-body radiation, a technique called blackbody infrared radiative dissociation (BIRD).