Ionisation innerer Elektronenschalen bei fast-adiabatischen Stößen schwerer Ionen

Abstract

Characteristic X-rays produced in nearly adiabatic collisions when fission products of 5–80 MeV energy are stopped in various materials have been studied using proportional counter detection. The cross sections for the ionization of inner electronic shells of both the colliding particles were measured as a function of the velocity and the mass of the fragments and the atomic number of the target atoms. The measured cross sections range from 10⁻²² to 10⁻¹⁶ cm². There is no agreement with the values predicted on the basis of a simple Born approximation description. Characteristic maxima were found in the dependence of the cross section on the atomic number of the projectile whenever the binding energy of the excited electron equals the electron binding energies of the various inner sheils of the projectile. The cross sections depend less strongly on the velocity of the projectiles than predicted by the simple theory. The measured X-ray quanta have energies from 1.2 to 11.4 keV. The observed energy values exceed the theoretical ones by about 0.10 keV for projectile atomic numbers >10. A qualitative explanation of the various effects is presented.