Excitation of AlK and HfM X-Ray Lines by 70-400-keV H+, He++, N++, O++, and Ar++ Ions

Abstract

The $K$ shell of aluminum and the $M$ shell of hafnium have been excited using H, He, N, O, and Ar ions in the energy range 70-400 keV. The appearance of an excitation mechanism is observed for N, O, and Ar projectiles, which results in ionization cross sections several orders of magnitude greater than those predicted by a direct-scattering interaction such as is assumed for H and He ions. The results are examined in the light of the electron promotion mechanism of molecular-orbital theory as suggested by Der et al. The similar increases in cross sections for the hafnium $M$ shell and the aluminum $K$ shell using incident ions heavier than He suggest that an electron promotion mechanism does not provide a satisfactory explanation of the anomalous cross sections. It is felt that other factors, such as polarization of the relevant atomic shells of both the target atom and the projectile at close impact distances, must be considered in terms of the direct-scattering theory.