The secondary emission from copper and silver films obtained with primary electron energies below 10 eV

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Abstract
An apparatus for the investigation of the secondary electron emission from freshly evaporated copper and silver films obtained with primary electron energies between thermal energies and 10 eV is described. The measured secondary emission ratios show a definite dependence upon primary electron energy which is different from that determined by previous workers. Furthermore, the values of the secondary emission ratio are lower than those hitherto recorded, both silver and copper possessing a secondary emission ratio less than 0·1 in the primary energy range 1 to 5 eV. The difference between the results presented in this paper and those obtained by earlier workers is attributed to the improved vacuum conditions which were used in the present work, thereby preventing the troublesome effects of contamination of the surfaces under investigation by the residual gases in the experimental tube. The energy distribution of the secondary electrons was measured and showed that at very low energies (less than 5 eV) these electrons are in fact elastically reflected primary electrons.