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 S-1-->n (1)L 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 omega(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/q omega(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.