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. Two senior JILA researchers, Alan Gallagher and Arthur Phelps, have spent a significant part of their careers studying the physics and chemistry of plasmas.

Gallagher's small 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.