High-intensity photochemistry in argon-ion and excimer laser-jets

Concerted reactions are usually classified as "forbidden" or "allowed" based on the symmetry of the orbitals involved, as described by the Woodward-Hoffmann rules. A reaction that is "allowed" in the ground state would be "forbidden"in the first excited state. However, in order for a reaction to proceed, the reaction must also be "allowed"energetically, i.e., there must be sufficient energy available and it must be in the proper form. Often the energy necessary, if introduced thermally, would destroy the molecule. When multiple photons are introduced into a molecule, the electrons will enter into the second excited state or possibly even higher. At this point, the molecule can enter a symmetry state that will 'allow' the molecule to react and the photons will provide the requisite energy. Compounds which may exhibit this type of reactivity have been explored.;In order to access the upper excited states of molecules a argon-ion continuous wave, laser-jet apparatus was used. It was designed to take advantage of the applification of light when interacting with microbodies. With significant modifications, the process has now been applied to an excimer laser. Some compounds that were previously unreactive in the argon-ion laser-jet apparatus were found to undergo photoreactions in the excimer laser-jet set up.