This book is devoted to Gas-Phase Thermal Reactions (GPTRs), and especially combustion reactions, which take place in engines, burners and industrial chemical reactors to produce mechanical or thermal energy to incinerate pollutants or to manufacture chemical substances, and which play an important part due to the consequences they have on the environment : fires and explosions, tropospheric pollution, greenhouse effect, hole in the stratospheric ozone layer. The design and running of engines, burners, incinerators, industrial reactors, both economical in fuels, raw materials and energy, efficient, safe and clean, as weIl as the scientific evaluation of the causes and the effects of atmospheric pollutions with a view to taking rational environmental decisions, which necessitate an understanding of the fundamental mechanisms of these reactions and an access to models allowing numerical simulations of the phenomena being studied to be carried out. The analysis of the results ofthe simulations then allows an optimal solution to be found to the industrial problem or to extrapolate the natural phenomena.

The book brings together, for the first time, all aspects of reactions of metallic species in the gas phase and gives an up-to-date overview of the field. Reactions covered include those of atomic, other free radical and transient neutral species, as well as ions. Experimental and theoretical work is reviewed and the efforts to establish a closer link between these approaches are discussed. The field is mainly approached from a fundamental point-of-view, but the applied problems which have helped stimulate the interest are pointed out and form the major subject of the final chapters. These emphasize the competition between purely gas-phase and gas-surface reactions.

The present monograph appears after the death of Professor V. N. Kondratiev, one of those scientists who have greatly contributed to the foundation of contem porary gas kinetics. The most fundamental idea of chemical kinetics, put for ward at the beginning of the twentieth century and connected with names such as W. Nernst, M. Bodenstein, N. N. Semenov, and C. N. Hinshelwood, was that the complex chemical reactions are in fact a manifestation of a set of simpler elementary reactions involving but a small number of species. V. N. Kondratiev was one of the first to adopt this idea and to start investigations on the elementary chemical reactions proper. These investigations revealed explicitly that every elementary reaction in turn consisted of many elementary events usually referred to as elementary processes. It took some time to realize that an elementary reaction, represented in a very simple way by a macroscopic kinetic equation, can be described on a microscopic level by a generalized Boltzmann equation. Neverheless, up to the middle of the twentieth century, gas kinetics was mainly concerned with the interpretation of complex chemical reactions via a set of elementary reactions. But later on, the situation changed drastically. First, the conditions for reducing microscopic cquations to macroscopic ones were clearly set up. These are essentially based on the fact that the small perturbations of the Maxwell-Boltzmann distribution are caused by the reaction proper.