The use of radiation chemical measurements to address the initial ener
gy deposition events of water radiolysis is discussed. Experiments tha
t probe both the number of ionisations in a spur and the average size
of the spur in radiolysis are detailed. The experimental results are c
ompared with present knowledge. The number of ions in a spur is consis
tent with the (large) range of calculated values. The spatial distribu
tion of an electron relative to the point of the initial ionisation is
determined by the loss of electron kinetic energy to vibrational mode
s of the solvent and not due to the energy loss to electronic states o
f the solvent. It is suggested that the use of a radiation chemical va
riable, such as spur number distribution and spatial distributions fro
m track structure calculations might facilitate the understanding of r
adiation damage mechanisms in biological systems.