1. The release of electrons from one solid material into another solid material.
2. The emission of electrons from one solid into another solid.
3. The process of injecting a beam of electrons with an electron gun into the vacuum chamber of a mass spectrometer, betatron, or other large electron accelerator.
4. The procedure used in forcing a beam of electrons into any large electron accelerator; such as, a beatatron by using an electron gun.