Pauli Excitation of Atoms in Collision

Experimental cross sections are reported for the ionization of $K$ shells of Al in collision with N, O, and Ar (in the energy range 100-300 keV); of Ne with C, Ne, and Al (100-300 keV); and of Al with Ne (0.1-3.2 MeV). They are some ${10}^3$ to ${10}^5$ times larger than the cross sections one predicts for Coulomb excitation of $K$-shell electrons by swift charged particles. The cross sections are determined by the exchange forces set up in the overlapping electron clouds of atoms in collision. This process is referred to as Pauli excitation.