ABSTRACT
Ionisation is the creation of ion pairs. This results from interactions that transfer energy
from the radiation to the atomic system. For energy transfers greater than electron binding
energies, electrons are ejected (see Section 1.4.2), leaving behind a positively charged ion. The
ability of ionising radiation to ionise a gas was one of its first properties to be observed; and
indeed, it is the defining property. The measurement of ionisation in a gas was also the basis for
the first radiation detectors.
