Ar:L Auger electron spectra from argon bombarded silicon have been investigated at projectile energies between 4 and 30 keV. The results indicate that excitation of argon is mostly due to argon-silicon collisions, in particular below 10 keV. Ar:L and Si:L2 excitation have been found to be closely related. The prominent Auger line at 212 eV is attributed to deexcitation of argon atoms slowing down in silicon. The line width increases with increasing projectile energy (Doppler broadening). © 1979.