Ionizing radiation

Ionizing radiation is a type of radiation which is sufficiently energetic to push an electron out of the outer shell of an atom. Because of this, the atom will in total have a positive charge instead of a neutral charge, the atom will be ionized, and becomes an ion. This type of radiation cannot be seen, heard, tasted, smelled or felt.

Ionization can occur in two ways: directly or indirectly. The direct way can only occur through charged particles, such as alpha particles or beta particles. The indirect way occurs in steps. An uncharged particle or a photon (electromagnetic radiation) starts a reaction with an atom or an atomic nucleus. Charged particles originate in this reaction, which then ionize other atoms.

The energy that a photon requires in order to ionize an atom depends on the type of atom. For example, hydrogen requires a photon with an energy of 13.6 eV (one electron volt = 1.602 10-19 joule) to be ionized, meaning radiation with a frequency of about 3.28 1015Hz, which corresponds with the frequency of ultraviolet light. Other values apply to other atoms.

Ionizing radiation exists in many different shapes, namely:

  1. particle radiation
  2. electromagnetic radiation

Examples of particle radiation are: alpha radiation, beta radiation (of β− electrons en β+ positrons), neutrons, protons. Electromagnetic radiation consists of photons, depending on the frequency it is either X-radiation or gamma radiation.

If you are unable to find what you seek, please don't hesitate to contact the Coördinating Radiation Expert (CSD) of HR.