Electron-Phonon Interaction in Alkali Halides. II. Transmission Secondary Emission from Alkali Halides

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Abstract
The phenomenon of secondary emission from alkali halides is studied in transmission. This allows the variation of one more parameter (thickness) than in conventional reflection studies. An empirical method based on published results of scattering by thin foils is used to determine the spatial dependence of the internal electron excitation function. The results of the Monte Carlo calculations presented in the previous paper (Part I) are used to generate a mathematical model of secondary emission. Measurements of pulsed secondary yield and of energy distribution of secondary electrons from uncharged films of CsI, KCl, NaF, and LiF are carried out at various film thicknesses and primary energies. By matching one single experimental point to the mathematical model, complete theoretical curves of yield for each material are generated. The results show that the spatial dependence of the excitation function taken together with the secondary escape results of Part I are sufficient to account for the variations of yield of different materials as a function of thickness and primary energy. An absorption attributed to d‐like conduction bands is experimentally observed in KCl. The energy dependence of the internal excitation function is obtained and it is also shown that it is incorrect to characterize the probability of escape of all internal secondaries by a single exponential. The implications and shortcomings of the experiments are discussed.