Charge states and effective loss cross sections for 33 TeV lead ions penetrating aluminum and gold foils

We consider the penetration of incident 33 TeV Pb 81+ (1s) and Pb 82+ ions through thin foils of aluminium and gold. We show that, due to the relativistic time dilatation, collision-induced excitations of the hydrogen-like lead ions inside the foils very substantially affect the projectile-electron loss process. Because of this the procedure of extracting loss cross sections from measured data on the fraction of hydrogen-like ions, which works quite well for modest relativistic impact energies, becomes questionable and, in particular, makes it impossible to extract accurate information about these sections from an experiment (Krause et al 1998 Phys. Rev. Lett. 80 1190) in which the penetration of 33 TeV Pb 81+ (1s) and Pb 82+ ions through foils was investigated.