Effect of Degree of Orientation and Crystal Size on the Scattering of 20-kev Electrons by Aluminum

The energy distribution of 20-kev electrons scattered by aluminum has been measured as a function of degree of crystalline orientation and foil thickness. For equal physical thickness the foils with higher degree of orientation are electron-optically thinner. Over a range of thickness from 35 to 500 A, the values of the first two characteristic losses are 6.3±{}0.1 ev and 15.0±{}0.1 ev. They exhibit no systematic change with thickness greater than the experimental uncertainty. The intensity ratio between the two losses is essentially constant within this range. It is concluded that the low-lying (6.3 ev) loss is not due to the depolarization effect of grain boundaries.