Approximate charge and transition energy cross-section scaling for excitation of atoms colliding with multicharged ions

Using the adiabatic theory and the dipole close-coupling and classical impulse approximations, scaling relations are derived for the cross sections of dipole-allowed and dipole-forbidden 1 ¹S→n ¹L excitation transitions in atoms induced by multiple charged ions of intermediate to high reduced energies. The cross-section scalings incorporate the ionic charge q, the electron transition energy ω_1n, and the oscillator strength (in the case of optically allowed transitions). The derived scalings describe well the available experimental data for H and He atoms for reduced energies E/qω_1n greater than about 25 keV/amu. These scalings also show that, for a fixed energy, the nonscaled excitation cross section as a function of q does not saturate at high q values but decreases after reaching a maximum. © 1996 The American Physical Society.