John Wiley & Sons, Inc. 1994. — 387 p.Chemical dynamics at low temperatures is connected with elementary reactions that surmount potential energy barriers separating reactants from products in the absence of thermal activation. The first experimental evidence of this type of reactions was obtained in the early 1970s in studies of solid-state conversion of free radicals. These investigations clearly demonstrated that there is a sufficiently sharp transition from Arrhenius-like exponential temperature dependence, characteristic of thermal activation, to much weaker power-like temperature dependence down to the low-temperature limit of the rate constant. In principle, the explanation of this phenomenon was known to be associated with tunneling through a barrier. Only after a substantial body of experimental data was accumulated were adequate models developed that elucidated the multidimensional character of tunneling and the effects of nontunneling intra- and intermolecular vibrational modes. Similar ideas have been considered independently in the quantum transition-state theory, which has been applied mainly to gas-phase reactions proceeding in the region below the energetic threshold. The supersonic jet cooling technique, in combination with high-resolution molecular spectroscopy, has revealed numerous examples of multidimensional tunneling in isolated molecules and dimers. There are a number of specialized reviews covering the advances in each of these separate areas of research, but there is now a need for a survey of the entire field. The joint consideration of multidimensional tunneling and its manifestation in the various branches of chemical physics can provide theoreticians with a guide to a huge set of yet unsolved problems to which modern quantum mechanical methods can be applied. Experimentalists need information about the deep analogies between tunneling phenomena taking place in a variety of fields that, at first sight, might seem unrelated. Our goal is to address both of these needs, which dictates the structure of the current volume and the choice of materials.Contents Introduction From Thermal Activation to Tunneling One-Dimensional Models Two-Dimensional Tunneling Chemical Dynamics in the Presence of a Heat Bath Hydrogen Transfer Tunneling Rotation Vibration-Rotation Tunneling Spectroscopy of Molecules and Dimers Heavy Particle Transfer
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