Primary photophysical processes
Photochemical rcactions originatc from specific electronically excited states and often the direction of a photochemical transformation depends critically on the nature of the rcacting statc. Nevertheless, ordinary photoreactions of polyatomic molccules have ground state products and their mechanisms must, therefore, include diabatic transitions from higher to lower potential energy surfaces. The possible nature of such processes is discussed and an attempt reportcd to observe electronically excited products. The role of the HellmannFeynman theorem in photochemistry is emphasized.