Most of the matter in our solar system, and, probably, within the whole
universe, exists in the form of ionized particles. On the other hand, in
our natural environ- ment, gaseous matter generally consists of neutral
atoms and molecules. Only under certain conditions, such as within the
path oflightning or in several technical devices (e. g. gas discharges,
rocket engines, etc. ) will some of the atoms and molecules be ionized.
It is also believed that the chemistry of the earth's troposphere
predomi- nantly proceeds via reactions between neutral particles. (The
complex system of atmospheric chemistry will be treated in one of the
forthcoming volumes to this series. ) Why, then, are ions considered so
important that hundreds oflaboratories all over the world (including
some of the most prestigious) are involved in research pro- grams on
ions, covering many different facets, from biochemistry to physics? One
may obtain as many different answers as there are research groups busy
in this field. There is, however, one simple, common feature which makes
it attractive to work with ions: since they carry one or more net
elementary charges, they can easily be gui- ded, focused or separated by
appropriate electric and magnetic fields, and, last but not least, they
can easily be detected. Apart from these advantages, which are welcome
and appreciated by the researcher, the study of molecular ions can
provide insight into very fundamental aspects of the general behavior of
molecules.