As mentioned in Section 4.4.2, electrons are emitted from the nuclei as a result of radioactive decay and from the electron orbitals. The electrons emitted from nuclei are called “beta particles.” Electrons emitted from the extranuclear shell are called electrons and are designated by e_. The two terms “beta particle” and “electron” differentiate the location of the emission. The main important difference is that

2 theta (degrees) distance of the crystal planes in Angstroms

beta particles have continuous spectra, while the electrons originating from the orbitals have discrete energy. Independent of their origin, the electrons and beta particles interact with the electrons and nuclear field of other atoms. The character­istic interactions are ionization, scattering (elastic and inelastic), and absorption.

The analytical applications of beta particles were described in Sections 5.3.4 and 5.3.6. Furthermore, the industrial applications using the scattering/reflection and absorption of beta radiation will be discussed in Section 11.3. In this section, the application of electron beams with discrete energy will be illustrated. The dis­crete energy means that these electrons are ejected from the electron orbitals. The energy of these electrons can be increased in accelerators.

The most important application of the electron radiation is the electron micro­scope. There are two types of electron microscope: transmission electron micro­scope (TEM) and scanning electron microscope (SEM). The image taken by each type of microscope originates from the electrons that were elastic scattered. Besides, electrons can transfer energy to the orbital electrons of the matter (inelas­tic scattering) and eject electrons from the K and L shells. The processes following electron ejection are the same as in the case of the photoelectric effect: Auger elec­trons can be emitted, or the vacancy can be filled with an electron from the outer shell. As a result, similar to XRF, characteristic X-ray photons are formed, which
can be used for qualitative and quantitative analysis. This process is used in electron microprobes.