Electron transfer and physical and chemical processes at low temperatures

We summarize some phenomena that occur at temperatures of the order of 15K, and are dominated by quantum mechanical tunneling. Although electron tunneling dominates many conduction processes at low temperatures, we discuss evidence that phenomena like oxidation, as well as the solution of alkali metals in ammonia, can also be dominated by electron tunneling. Both phenomena demonstrate that the chemical potential of a metastable system can equilibrate at low temperatures by electron tunneling. The case of alkali metal clusters covered with ammonia is contrasted to covering the clusters with Xe. In this case changes in the activated conduction are observed which are consistent with the dielectric constant of the rare gas