A new film‐bulk method is used for the measurement of the depth distribution of current density and absorption of incident primary electrons penetrating into solid targets of Be, Al, Cu, and Au, As well the depth dependence of the generation of secondary electrons in the interior of the targets is determined experimentally. The energy transfer curves resulting from the inelastic multiple scattering of the primary electrons show a maximum at the depth x0(E0). This makes possible the quantitative volume spectroscopy by a beam of primary electrons of variable energy E0.

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Further investigations of our retarding potential measurements reported in (1) showed that the energy of emitted electrons can achieve values up to 80 eV. Earlier attempts of several authors for the interpretation of the exo-electron emission (2 to 6) cannot explain these high energies. Therefore a new model shall be proposed in this paper.If insulating materials are bombarded with electrons of an energy at which the > 1, the surface will be charged posi-secondary electron emission coefficient tively. Because of the interaction of the primary electrons with the solid they only penetrate to a certain depth. In the region of maximal penetration depth of the primaw electrons their energy is so small that they will be captured by traps. A negative space charge region is built up. Because of the high-resistive material no neutralization of charges will take place. The generated electric field between the negative space charge region and the positive surface layer effects an equilibrium state at which in equidistant time intervals the same number of traps are emptied and occupied. In the region between negative space charge and positive surface no traps are occupied, because electrons just being trapped are released immediately by subsequent electrons into the conduction band, from where they are removed by the internal electric field. Electrons which are thermally released into the conduction band can leave the solid, if they are able to overcome the energy barrier at the surface and compensate the energy loss caused by scattering processes along the way to the surface. The average energy loss of an electron per scattering process amounts to 0.03 eV, the mean free path to 5x10 cm (7). If the strength of the electric field exceeds 10 V/cm the energy loss of a scattered electron is smaller than the energy gain along the mean free path. -7 5We assume that the emission process only takes place if insulating surface layers are present. Then the emission process takes the following course (see

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