Nondipole channels in the electron-energy-loss structure near the 3<i>s</i> edge of copper

Electronic transitions near the 3<i>s</i> edge of copper are investigated with electron-energy-loss spectroscopy and compared with real-space multiple-scattering calculations. Calculating the generalized oscillator strength illustrates the importance of dipole-forbidden transitions in the near-edge region and shows for the first time the feasibility of making detailed comparisons between theory and electron-energy-loss measurements without resorting to the dipole approximation.