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| Ionisation | |
|---|---|
| Name | Ionisation |
| Type | Physical process |
| Field | Chemistry; Physics |
Ionisation
Ionisation is the process by which an atom, molecule, or cluster loses or gains one or more electrons, producing charged species such as cations or anions. It underpins phenomena across Antoine Lavoisier-era chemistry, Albert Einstein-era photoelectric studies, and modern Marie Curie-linked radioactivity, and is central to technologies developed at institutions like Bell Labs and CERN. The process connects laboratory techniques from Sir J. J. Thomson's cathode-ray experiments to instrumentation used at facilities such as Lawrence Berkeley National Laboratory and Max Planck Institute research groups.
Ionisation converts neutral particles into ions by altering electronic structure through energy transfer or chemical reaction; it is foundational to observations in Isaac Newton-era optics, Michael Faraday-era electrochemistry, and Niels Bohr-style atomic models. Historical milestones include experiments by Eugen Goldstein and William Crookes, theoretical framing by Erwin Schrödinger and Paul Dirac, and applications at national labs like Los Alamos National Laboratory and industrial settings such as Siemens. Ionisation energies and cross sections are tabulated by organizations like National Institute of Standards and Technology and used in models by groups at Massachusetts Institute of Technology and Imperial College London.
Electron removal or attachment occurs via distinct mechanisms: photoionisation initiated by photons, collisional ionisation via energetic particles, and field ionisation in intense electric fields. Photoionisation traces to phenomena explored by Heinrich Hertz and quantified in works by Robert Millikan, with modern sources from Fermi National Accelerator Laboratory synchrotrons. Collisional ionisation appears in plasmas studied at Princeton Plasma Physics Laboratory and in beam interactions at SLAC National Accelerator Laboratory. Field ionisation underpins operation of devices developed at General Electric and research at Tokyo Institute of Technology.
Quantum mechanical descriptions employ models from Werner Heisenberg and Paul Dirac with computational implementations at centers like Lawrence Livermore National Laboratory and Argonne National Laboratory. Semi-classical rate theories derive from contributions by Enrico Fermi and Hendrik Kramers, used in simulations by groups at California Institute of Technology and ETH Zurich.
Common classes include photoionisation, thermal ionisation, chemical ionisation, impact ionisation, Penning ionisation, and autoionisation. Photoionisation is exploited in devices developed by Philips and research at Stanford University; thermal ionisation appears in geological dating methods refined at University of Cambridge isotope labs. Chemical ionisation is central to mass spectrometry techniques from Thermo Fisher Scientific and pioneered in work involving Franz Hillenkamp. Impact ionisation occurs in gas-discharge lamps popularized by Georges Claude and in detectors used by European Organization for Nuclear Research. Penning ionisation relates to noble-gas interactions studied at University of Chicago and University of Oxford laboratories. Autoionisation processes were characterized in spectroscopy research by John Hasbrouck van Vleck and later at Rutherford Appleton Laboratory.
Ionisation energies and rates are quantified in electronvolts (eV), reciprocal seconds (s−1), and cross sections in square centimeters (cm2). Standard compilations from National Physical Laboratory and NIST provide benchmarks. Experimental techniques include mass spectrometers engineered by Waters Corporation, ionization chambers used in radiotherapy at Mayo Clinic, and cloud chambers originally developed by Charles Thomson Rees Wilson. Detection methods use Faraday cups at accelerators such as TRIUMF and charge-coupled devices from NASA missions.
Ionisation probabilities depend on ionisation potential, photon energy spectra produced by sources like European Synchrotron Radiation Facility, particle fluxes from accelerators like Brookhaven National Laboratory, and local electric fields in devices from Tesla, Inc. and Siemens. Environmental conditions—temperature, pressure, and medium composition—play roles in processes observed at Scripps Institution of Oceanography and United States Geological Survey isotope facilities. Surface work functions studied by Arthur Schuster and electronic structure computed at Max Planck Institute for Quantum Optics influence field and contact ionisation phenomena.
Ionisation enables mass spectrometry platforms used in pharmaceuticals by GlaxoSmithKline and proteomics at European Molecular Biology Laboratory, ion propulsion systems developed by NASA and Aerojet Rocketdyne, and plasma processing in microfabrication by firms like ASML. Medical imaging and radiotherapy at institutions such as Johns Hopkins Hospital and Memorial Sloan Kettering Cancer Center exploit ionisation detectors and dosimetry standards from International Atomic Energy Agency. Atmospheric and space science measurements are conducted by instruments on missions from European Space Agency and Roscosmos. Ionisation underlies semiconductor doping researched at Intel and IBM.
Ionising events drive radiation biology studied by researchers at Cold Spring Harbor Laboratory and Francis Crick Institute; they cause DNA damage, oxidative stress, and mutagenesis in contexts examined following findings by Hermann Joseph Muller and Marie Curie-era radiobiology. Environmental ionisation from cosmic rays monitored by University of Chicago and NOAA affects atmospheric chemistry relevant to studies by Intergovernmental Panel on Climate Change. Regulatory frameworks and safety standards are set by International Commission on Radiological Protection and enforced by agencies like Environmental Protection Agency and European Commission-linked bodies.