ionize

Ionize is the verb meaning to convert a neutral atom or molecule into an ion by adding or removing electrons. In most contexts, ionization refers to removing one or more electrons, producing positively charged ions (cations), though electrons can also be added to form negatively charged ions (anions). The energy required to remove an electron is called the ionization energy.

Ionization occurs through several common mechanisms. Electron-impact ionization happens when high-energy electrons collide with a target atom or molecule and eject electrons. Photoionization uses photons with sufficient energy to overcome the ionization threshold. Field ionization involves strong electric fields that pull electrons away from atoms. In gases, chemical or charge-transfer ionization can occur during reactions where ions are produced as intermediates or products. In mass spectrometry, advanced techniques such as electrospray ionization and matrix-assisted laser desorption/ionization deliberately generate ions from analyte molecules for detection.

Ionization is central to many scientific and technological fields. It underpins analytical chemistry and mass spectrometry, where ions are measured to identify and quantify substances. It also plays a key role in plasma physics, semiconductor processing, and radiation chemistry, where ionized species drive chemical and physical changes. In astrophysics and atmospheric science, ionization of gases by ultraviolet radiation and energetic particles helps govern the behavior of plasmas and the structure of the interstellar medium.

Ionizing radiation refers to radiation energetic enough to remove electrons from atoms, including X-rays and gamma rays. Non-ionizing radiation, such as visible light and radio waves, lacks sufficient energy to ionize under normal conditions.