Abstract
A systematic review of modern views on the factors which favour the formation of chemical reaction products with greater equilibrium excitation is presented. The excitation can be electronic (for reactions in solution) or electronic and vibrational (for gas-phase reactions). In the latter case, fine details can be revealed, and particular features of the excitation process can be related to the electronic structure of the reactants (atoms or simple molecules). With complex molecules (typical of liquid-phase reactions) only a qualitative or semi-quantitative interpretation is possible. Examples are chosen from among those reactions whose chemiluminescence is adequately understood. Although the excitation mechanism is specific for a particular reaction type, excitation is favoured in general by the participation of ions, radical-ions, and charge-transfer states; these species also favour the retention of the reaction energy as internal energy of the products. 119 references.