Ratios of ionization cross sections for proton impact to those for He-ion3 impact have been measured on Al K and Y L shells at projectile energies of 7, 9, 12, 16, and 21 MeV /amu. The ratio tends to unity with an increase in the projectile energy for both the Al K and Y L ionizations. This behavior can well be explained in terms of the Binstock-Reading theory combined with the distant-collision theory of Hill and Merzbacher: The polarization effect in distant collisions and the decreasing electron-density effect in close collisions cancel out each other in this high-energy region.
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics