We evaluate electron excitation spectra generated by slow ions in an electron gas. Energy and angular spectra, and total excitation rates, are given. Non-linear screening effects on the intruding chargeZresult inZoscillations in the spectra of electron excitations and in the total excitation rate. Predictions are given, for different electron gas densities, using phase shifts obtained from numerical self-consistent solutions of the Kohn-Sham density-functional formalism. The results are compared with those obtained in the linear dielectric response, and with the pseudopotential model of target response. The connection between electron excitation spectra and ion energy loss parameters (stopping power and straggling) is discussed.