Electron-loss cross sections, for 20-MeV ${\mathrm{Cl}}^{4+}$ and ${\mathrm{I}}^{5+}$ ions incident on thin gaseous targets: Experimental measurements and potential-model data analyses

Differential cross sections for charge change resulting from the scattering of 20-MeV ${}_{}{}^{127}{}_{}{}^{}\mathrm{I}_{}^{5+}{}_{}{}^{}$ and 20-MeV ${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}_{}^{4+}{}_{}{}^{}$ ions from thin gaseous targets have been measured. Total cross sections for multiple-electron loss have been determined by integration of the differential charge-state yields over angle. Cross sections are presented for ${}_{}{}^{127}{}_{}{}^{}\mathrm{I}_{}^{5+}{}_{}{}^{}$ ions and ${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}_{}^{4+}{}_{}{}^{}$ ions on Xe, Ar, and ${\mathrm{N}}_2$. Impact-parameter analyses of charge-fraction data have been performed; these analyses depend on the assumed interatomic potential but not on any absolute measurements. The applicability of Bohr, Thomas-Fermi, and Lenz-Jensen potentials was examined. The Bohr potential gave unsatisfactory fits to the directly measured cross sections for all observed collisions with impact parameters greater than about three times the screening radius. For the cases reported here, the Thomas-Fermi and Lenz-Jensen potentials tend to give underestimates of the total cross sections, probably because they do not take into account the ionized nature of the collisions partners.