Comment on range distributions of energetic ions in matter

The relative effects of electronic and nuclear collisions on the shape of the longitudinal ion-range distribution have been examined for incident ion energies well above the stopping-power maximum. At these higher energies the parameter ${\left({\sigma }_{\parallel }\right)}_n$ calculated by Littmark and Ziegler is shown to be of little practical significance. Agreement between the calculated value of ${\left({\sigma }_{\parallel }\right)}_n$ and an experimental measurement quoted by Littmark and Ziegler is shown to be fortuitous.