Total Cross Sections for Formation of Ions from CsBr by Collision with Ar, Xe, and NaBr(Ar)

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Abstract
Measurements have been made by cross beam techniques on the absolute total cross section Q for formation of ions from CsBr in collisions with Ar and Xe, and relative total cross section for NaBr with Ar, in a range of relative kinetic energies (Xe: 12–120 eV; Ar: 20–125 eV). The absolute cross sections obtained for CsBr, with estimates of accuracy, are 5.0±1.2 Å2 for Ar and 12.6±2.7 Å2 for Xe at a relative kinetic energy of 46 eV. The energy dependence of the cross sections follows closely that predicted by the simple reactionmodel of hard spheres. A fit of this model to the measurements leads to estimates of threshold energies. Measurements have also been made on a crude energy analysis of the ions formed. About half the ions of either sign have laboratory energies below 5 eV and the remainder is distributed continuously over larger energies up to the maximum. Negative ions have somewhat lower energies than positive ones. The results are consistent with a knockout model of collisional dissociation to ions, with a preference for dissociation by collision of the rare gas atom with the heavy (positive) end of the molecule.