Photochemical production of trapped electrons in solutions of polyhalogenomethanes in hydrocarbon glasses

It is suggested that the colour centres produced when frozen hydrocarbon solutions containing dissolved polyhalogenomethanes are exposed to near-ultraviolet light are associated with trapped electrons. It is shown that the same colour centres can be produced by photosensitisation with readily photo-oxidised aromatic amines. Charge-transfer complex formation is shown to be an important process in the frozen solutions, and it is suggested that charge transfer, either in the absence or presence of sensitisers, is responsible for the formation of the trapped electrons. The nature of the trapping sites is discussed, and these are probably due to aggregates of solute molecules, frozen in the glassy solution.