Plasmachemie

Plasmachemie, or plasma chemistry, is the branch of chemistry that studies chemical processes in plasmas, i.e., ionized gases in which electrons, ions, and neutral species interact. Unlike conventional gas-phase chemistry, plasma chemistry must account for energetic electrons, metastable species, and rapid, non-equilibrium reactions driven by electric fields and energy transfer.

A central concept is non-equilibrium plasmas, where the electron temperature can be much higher than the temperature of heavy species. Reactive species such as atomic and molecular radicals, ions, excited states, and photons govern the chemistry. Key reaction types include electron-impact ionization and excitation, ion-molecule reactions, recombination, and surface interactions with materials.

Generation and study of plasmas rely on various techniques. Electrical discharges (glow discharge, dielectric barrier discharge, radio-frequency or microwave plasmas), plasma jets, and pulsed plasmas are common sources. Characterization and modeling use tools such as optical emission spectroscopy, mass spectrometry, laser-induced fluorescence, and plasma-fluid or kinetic simulations.

Applications span materials processing, semiconductor manufacturing, and surface engineering, including plasma-assisted synthesis, plasma-enhanced chemical vapor deposition, etching, and surface modification. In environmental and energy contexts, plasmas enable pollutant destruction, CO2 conversion, and catalytic or photochemical processes. Medical and sterilization uses are also explored.

The field is highly interdisciplinary, combining chemistry, physics, and chemical engineering, with emphasis on reaction networks, radical kinetics, and diagnostic methods. Historically, early work by Irving Langmuir and colleagues on ionized gases helped establish plasma chemistry as a distinct discipline, linking laboratory plasmas to chemical reactivity.