Statistical Model for theAr+-on-Ar Collision

Abstract

This paper introduces a model to describe and predict the preceding experimental results on ${\mathrm{Ar}}^{+}$—Ar scattering. In considering a number of collisions in a data set it is assumed that there is a distribution among the inelastic energies of the atoms after the collision. It is further assumed that the energy received by one atom is not correlated with the energy received by the other atom in the same collision. The model, whose distribution widths are fitted to the data, predicts the average inelastic energy loss ${\overline{Q}}_{\mathrm{mn}}$ associated with a collision which results in one atom becoming $m$ times ionized and the other $n$ times ionized. The relative abundance ${\overline{p}}_{\mathrm{mn}}$ of the ($m, n$) reaction is also predicted. The values of ${\overline{Q}}_{\mathrm{mn}}$ and ${\overline{p}}_{\mathrm{mn}}$ so predicted agree well with the data. The model allows derivation from the data of the probability $P_i$ that an atom, which received a particular inelastic energy $E$, subsequently becomes $i$ times ionized. These derived $P_i\mathrm{}\left(E\right)\mathrm{}$ curves are rather similar in form to those which have been calculated by Russek. Under some circumstances there is a triply peaked structure to the inelastic energies transferred in these collisions. This structure is explained within the framework of the present model. Indirect evidence is presented that in the more violent collisions there may be one fast electron emitted per atom whose kinetic energy is a sizeable fraction of the inelastic energy.