The single-electron detachment (SED) cross sections for Co− and Ir− in collision with Ar in the energy region of 10–30 keV are obtained in our laboratory. As our previous paper reported, the SED cross sections have velocity and electron affinity dependency. Using the least-squares method, we analyze the available experimental data of SED cross sections for different negative ions in collision with Ar, and get empirical formulas for different sets of anionic projectiles. For most anionic projectiles, there is a clear correlation between increasing electron affinity and decreasing SED cross sections. Co and Ir, however, are an exception, and we discuss how other physical parameters can be taken into account in the search for general scaling rules for SED cross sections. As the incident velocity increases, the cross section dependence of the anion's electron affinity becomes weaker, and the relation between the SED cross sections and νp is supposed to be [Formula: see text].
