The contribution of surface electron-hole pair creation processes to the nonradiative relaxation of the C 3Πu electronically excited state of N2 on Al(111) is investigated using electron energy loss spectroscopy. The homogeneous broadening of the spectral lines is found to be ∼ 140 meV, corresponding to a lifetime of ∼ 5 × 10 -15s. We compute the contributions of surface and bulk electron-hole pair generation processes to the lifetime broadening, utilizing a theory for the nonlocal dielectric response of the metal based on the Lang-Kohn model for the surface potential. The theory predicts correctly the observed overall decay rate and shows that surface processes make an order of magnitude higher contribution to that rate than the bulk processes. The physical conditions which determine the relative importance of surface and bulk processes are discussed. © 1983 American Institute of Physics.