The projectile-energy dependence of Si-LMM Auger electron emission and Si2+ and Si3+ secondary ion emission from silicon has been measured in situ for bombardment with 2-30 keV Ne, Ar, Kr, and Xe ions at an angle of incidence of 45°. Si2+ and Si3+ emission has also been studied at normal incidence. It was found that all signals increase very rapidly with increasing projectile energy, I ∝ En, with n up to 5. The low energy threshold, Eth, depends upon the maximum energy transfer between primary ion and target atom. The intensities of Auger electrons and multiply charged secondary ions are directly proportional to each other. Si2+ and Si3+ are thus produced as a result of Auger deexcitation of sputtered Si ions containing a 2p hole. Excitation is mostly due to symmetric SiSi collisions in the bulk. Additional excitation due to direct projectile-target interaction is observed in the case of Ar impact. The intensity ratios I(45°)/(I(0°) for Ne, Kr, and Xe bombardment increase by a factor of three between 3 and 10 keV. © 1980.