Electron sources HREELS

Figure 2 The necessary part of an HREELS spectrometer e, electron source, L, lens to focus electrons onto the entrance slit of the monochromator, M, which can have one or two stages. Another lens, L, focuses the beam onto the sample, S. A lens, L, focuses electrons scattered from the surface onto the entrance slit of the analyser, A which can also have two stages. The electrons are counted at the detector, D.

High resolution electron energy loss spectroscopy (HREELS) is a form of surface vibrational spectroscopy in which the difference in energies between an impinging and a scattered electron beam provides information about the vibrational modes of a surface species. The apparatus is similar to that used in AES, in that an electron beam serves as the excitation source. However, because one must make precise measurements with resolutions in the meV range, the excitation electron beam is made monochromic to within... 

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