Dispersion of Solid State Excitations

Abstract

The addition of an electron spectrometer to an electron microscope extends the capabilities not only of the microscope but also of the electron spectrometer. Operation of the electron microscope in the high angular resolution, small angle scattering mode (see, for example, Wade and Silcox) extends the angular scattering range of the electron spectrometer into an interesting small angle region (<10−4 radians) hitherto inaccessible. The dispersion of many solid state excitations in the energy range leV to 20eV is strongly affected by the light line w = ck where the energy loss ΔE = ђw and the momentum transfer is ђk. These effects can be observed directly by the electron microscope/spectrometer combination at scattering angles <10-4 radians.