Cathodoluminescence, luminescence that arises when a phosphor is excited by an electron beam (cathode rays); one of the forms of radioluminescence. Gases, molecular crystals, organic phosphors and crystal phosphors are all capable of cathodoluminescence, but only crystal phosphors withstand the action of an electron beam and give a sufficient brightness of emission, and they are therefore the ones used as cathodoluminescent phosphors.
Cathodoluminescence is excited even at electron energies 1.5 times the ionisation potential of the atoms of the crystal phosphor, but beams of electrons with an energy above 100 eV are usually used to excite it. Electrons of such energies overcome the potential barrier associated with the surface charge of the crystal and knock out secondary electrons, which in turn ionise other atoms of the phosphor's crystal lattice. This process continues as long as the energy of the ejected electrons is sufficient to ionise atoms. The holes formed by the ionisation migrate through the lattice and can be passed to the luminescence centres. Cathodoluminescence arises when holes and electrons recombine at these centres. The spectrum of cathodoluminescence is similar to that of photoluminescence; its efficiency is usually 1—10% of the energy of the electron beam, the greater part of which turns into heat.
Cathodoluminescence is used in vacuum electronics (the glow of television screens, of various oscilloscopes, of image converter tubes and so on). The phenomenon of cathodoluminescence underlies the creation of lasers pumped by an electron beam.
Cathodoluminescence is excited even at electron energies 1.5 times the ionisation potential of the atoms of the crystal phosphor, but beams of electrons with an energy above 100 eV are usually used to excite it. Electrons of such energies overcome the potential barrier associated with the surface charge of the crystal and knock out secondary electrons, which in turn ionise other atoms of the phosphor's crystal lattice. This process continues as long as the energy of the ejected electrons is sufficient to ionise atoms. The holes formed by the ionisation migrate through the lattice and can be passed to the luminescence centres. Cathodoluminescence arises when holes and electrons recombine at these centres. The spectrum of cathodoluminescence is similar to that of photoluminescence; its efficiency is usually 1—10% of the energy of the electron beam, the greater part of which turns into heat.
Cathodoluminescence is used in vacuum electronics (the glow of television screens, of various oscilloscopes, of image converter tubes and so on). The phenomenon of cathodoluminescence underlies the creation of lasers pumped by an electron beam.