Ionization

Ionization is the process by which a neutral atom or molecule acquires a positive or negative electrical charge by gaining or losing electrons. It is the foundational step in mass spectrometry, plasma physics, and atmospheric chemistry, transforming neutral matter into charged species that can be manipulated by electric and magnetic fields.\n\nThe physical mechanisms of ionization span a wide range of energies and environments. Electron impact ionization, the classical method, uses high-energy electrons to knock valence electrons from molecules. Electrospray ionization, developed by John Fenn in 1984, produces ions from solution-phase molecules and revolutionized the analysis of large biomolecules. Matrix-assisted laser desorption ionization (MALDI) uses laser energy absorbed by a matrix to vaporize and ionize large, fragile molecules without fragmentation.\n\nEach ionization method produces a characteristic fragmentation pattern that encodes structural information about the parent molecule. The pattern is not arbitrary; it reflects the molecular topology, bond strengths, and energetics of the ionization process. Understanding fragmentation is therefore a problem of inverse inference: given the observed ion distribution, what molecular structure produced it?\n\n\n\n