The Origin of the Characteristic Electron Energy Losses in Ten Elements

Abstract

Measurements have been made of the characteristic electron energy loss spectra of beryllium, antimony, bismuth, germanium, tin, cadmium, copper, platinum, lead and calcium using the reflection technique and with 750 eV and 1500 eV primary electrons. The spectra of each element were found to consist almost entirely of combinations of two fundamental energy losses which were identified as plasma and lowered plasma losses. A striking correlation between the lowered plasma losses and the corresponding calculated values of hω_p/radical2 was observed (ω_p is the plasma frequency), and it is suggested that the magnitude of the lowered plasma loss may be useful as an indication of the effective free electron density. If the specimen oxidized appreciably, the intensity of the lowered plasma loss decreased rapidly and a new modified lowered plasma loss appeared. It is considered that the present results are characteristic of clean metal surfaces and that many of the discrepancies in past work can be explained by the presence of surface contaminants.