Plasma, or hot ionized gas, is a distinct phase of matter. Atomic and molecular behavior in plasma is often unique, as are many chemical reactions. One of these unique plasma reactions is the dissociative recombination of H₃⁺ , which has until now exhibited a different reaction rate in plasma than it has in experiments performed at Sweden’s CRYRING storage ring and Germany’s Test Storage Ring. The storage-ring reaction rates correspond well with the theory of dissociative recombination of H₃⁺ developed by Chris Greene and V. Kokoouline of the University of Central Florida. The puzzle has been figuring out what’s different about this reaction in plasma.

The mystery was recently solved in a study of the dissociative recombination of H₃⁺ in a room-temperature plasma consisting of helium (He), argon (Ar), and hydrogen (H₂). Experimentalist J. Glosík and his co-workers at Charles University in Prague, in collaboration with Greene and Kokoouline, found that an additional 3-body recombination process mediated by the He buffer gas was responsible for the rate discrepancy. Greene’s and Kokoouline’s calculations of the rate of the newly discovered 3-body H₃⁺ dissociative recombination process mirrored the new experimental results.

Hydrogen Plasma Emission.

Credit: Sandpiper at en.Wikipedia

Investigations of the physics and chemistry of plasmas have been a significant part of the careers of two senior JILA researchers, Alan Gallagher and Arthur Phelps. Gallagher's research program focuses on the plasmas used to deposit thin films of silicon on steel or glass to create the large-area semiconductors used in liquid crystal displays and photovoltaic arrays. In these deposition plasmas, an electric discharge breaks up stable, silicon-containing molecules, forming neutral radicals and ions that deposit on the surfaces, building up the device layer by layer. Gallagher studies the type and behavior of these reactive components and the plasma and surface chemistry affecting the device properties. His studies clarify the characteristics of chemically complex plasmas and guide industrial research and development of thin-film devices.

Phelps is currently investigating the consequences of energetic collisions between hydrogen atoms and molecules in plasmas. These entities can have enough energy that they emit light when they collide. Phelps analyzes the emitted light to determine the presence and energy of the fast atoms and their precursor ions in the plasma. By clarifying experiments and compiling data on plasma collisions in hydrogen and other gases, this work has led to the recognition of the role of fast, neutral atoms in laboratory and industrial plasma devices.

The content provided by Answer Tips does not come from JILA or NIST, but from other sources. Any content provided by Answer Tips within JILA or NIST web pages is for information only; it does not imply recommendation or endorsement by JILA or NIST.