Competition of Predissociation Processes in the Photolysis of Polyatomic Molecules

It is shown that if a photoactivated polyatomic molecule may decompose in more than one way with different products for each path, certain generalizations govern the probability of an activated molecule decomposing by any given path. First, there is a tendency to form those products which require a minimum amount of the activation energy to appear as kinetic energy. This tendency increases with increase in energy of the molecule if the energies at which the different paths become possible are widely separated but the opposite effect is found if the separation is small. The effects of collisions in causing predissociation is shown to be interpretable partially as an alteration of the number of times that the molecule reaches a condition represented by the intersection of two hypersurfaces and partially as a disturbance of the restrictions existing at such crossings. These principles are applied in a discussion of the photolyses of acetone, acetaldehyde, acetic acid, formic acid, and normal butyraldehyde.