ionisaation

Ionisaation, or ionization, is the process by which atoms or molecules acquire a net electric charge by the loss or, less commonly, gain of electrons. In chemistry and physics, ionization is usually described as the removal of one or more electrons from a neutral species, producing a cation, or in some contexts, the addition of electrons to form an anion.

Ionization can occur through various mechanisms. Photoionization uses photons with sufficient energy to overcome ionization thresholds. Collisional ionization occurs when energetic particles collide with atoms, common in high-temperature plasmas. Field ionization uses very strong electric fields to strip electrons. Chemical ionization in mass spectrometry involves reactions that generate ions indirectly. Ionization energies increase with each successive electron removed, and the energy required differs among elements and molecules.

Ionized species are central to plasma physics, astrophysics, and analytical chemistry. In gases, sufficient ionization leads to plasma, with free electrons and positive ions. Ionization states are described by the charge, such as singly ionized (1+), doubly ionized (2+), etc. Ionization can occur in environments ranging from stellar atmospheres to flames and electrical discharges.

Applications include mass spectrometry for chemical analysis, lighting and discharge devices, semiconductor manufacturing, and radiation shielding considerations. The study of ionization also informs understanding of chemical reactivity and the behavior of matter under extreme conditions.