Abstract
The spontaneous decay of chemically bound radioactive atoms affords a route to ions of well-defined structure and charge location, free of counterions. The nuclear nature of the ionization process makes it insensitive to environmental effects, so that exactly the same charged species can be generated, and its reactivity investigated, in widely varying media, from low-pressure gases to liquids and solids. Techniques based on nuclear decay are used in studies of the production of otherwise inaccessible species, the structural characterization of free ions, and the comparative evaluation of their reactivity in different environments, in particular, gas phase and solution.