Low-energy electronic stopping cross sections in nitrogen and argon

Abstract

The rate of energy loss in nitrogen and argon targets for ions with [Formula: see text] and E < 200 keV has been measured. The contribution to the energy loss from nuclear stopping was calculated using Fastrup's method, and was subtracted from the observed stopping cross section to give the electronic stopping cross section. Over the energy interval studied, the electronic stopping cross sections obtained are below the theoretical values and the energy dependence in argon is much greater than [Formula: see text].A target gas pressure of ~10 μ was used. This reduces the collision frequency eight orders of magnitude below that in a solid. The periodic dependence of the electronic stopping cross section on the atomic number of the incident projectile, previously observed in solid targets, occurs also for such low-pressure gas targets; it is concluded that this dependence is not affected by the collision frequency.