Ionization by protons in the energy range 100 to 450 keV has been investigated by means of the well-known parallel-plate condenser method. A uniform axial magnetic field enables slow ion collection to be carried out over a precisely determined path length at pressures low enough to ensure single collision conditions. The total cross-section for slow ion production cr+, and the total ionization cross-section have been determined for protons in hydrogen, helium , neon, argon and krypton. It is found that charge transfer is very small above about 200 keV so that cr+ ~ cr
e
. The ionization cross-section for all cases falls off as E
-1
log
E
where
E
is the energy of relative motion. At the high-energy limit of the present measurements, the proton ionization cross-sections agree closely with electron ionization cross-sections for the same relative velocity of impact. The results are therefore in agreement with the general predictions of the Born approximation.
High energy PIXE: New experimental K-shell ionization cross sections for silver and gold and comparison with theoretical values from ECPSSR/RECPSSR models