Ionization
![Avalanche effect between two electrodes. The original ionization event liberates one electron, and each subsequent collision liberates a further electron, so two electrons emerge from each collision: the ionizing electron and the liberated electron.](/Images/godic/202501/20/Electron_avalanche4313.gif")
![Figure 1. Ionization energies of neutral elements.](/Images/godic/202501/20/First_Ionization_Energy.svg4313.png")
![Combined potential of an atom and a uniform laser field. At distances r<r0, the potential of the laser can be neglected, while at distances with r>r0 the Coulomb potential is negligible compared to the potential of the laser field. The electron emerges from under the barrier at r = Rc. Ei is the ionization potential of the atom.](/Images/godic/202501/20/Tunnel_ionization_34314.png")
![The schematic presentation of lambda type population trapping. G is the ground state of the atom. 1 and 2 are two degenerate excited states. After the population is transferred to the states due to multiphoton resonance, these states are coupled through continuum c and the population is trapped in the superposition of these states.](/Images/godic/202501/20/Lambda_type_population_trapping4314.png")
Ionization is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons to form ions, often in conjunction with other chemical changes. Ionization can result from the loss of an electron after collisions with subatomic particles, collisions with other atoms, molecules and ions, or through the interaction with light. Heterolytic bond cleavage and heterolytic substitution reactions can result in the formation of ion pairs. Ionization can occur through radioactive decay by the internal conversion process, in which an excited nucleus transfers its energy to one of the inner-shell electrons causing it to be ejected.