LEAF, Chemistry's Newest Branch

With the construction of the Laser-Electron Accelerator Facility (LEAF) at Brookhaven, the Lab’s Chemistry Department has begun research in many exciting areas.
LEAF is a key component of the department’s Center for Radiation Chemistry Research, which aims to closely study chemical reactions by bombarding samples with tiny clusters of high-energy electrons. This technique allows scientists to “see” chemical processes that occur on very, very short time scales.

Loading a sample into LEAF for analysis

Chemists working at LEAF are currently working on several cutting-edge research projects, and plan to delve into others. Materials they are studying, or plan to study, include:

• Ionic liquids ­— organic liquid salts with very interesting properties. For example, they remain in a liquid state over a wide range of temperatures, are exceptionally good solvents, and do not produce any measurable amount of vapors. They may become environmentally friendly replacements (called “green” solvents) for many harsh chemical solvents now used in industry.

• Aryl Halides — a class of molecules containing one of the “halogen” elements (fluorine, chlorine, bromine, iodine, and astatine) bound to a six-carbon, six-hydrogen ring molecule, known as a benzene ring. Studying how the halogen atom breaks away from the benzene ring, an extremely quick event, is a good way to learn about very fast bond-breaking reactions, which underlie the manufacture of many industrial products. These studies may, as a result, help improve the efficiency of and reduce the waste associated with industrial production.

• Dendrimers — a class of polymer molecules characterized by their unusual struc-ture: multi-branch “limbs” radiating from a central core, somewhat like a tree with no trunk. Certain members of the dendrimer family are unusually good at storing light energy. When they absorb light, the electrons in the branches become energized and move to the central core, where they cluster for long periods of time. With further study of this behavior, dendrimers could be incorporated into efficient solar-energy systems.