The basic theory of how chemical reactions happen--molecules approach each other, overcome potential energy, and then form new reactants--has held up in experiments almost every time. But the theory doesn't fully explain what happens when a molecule approaches a metal surface, such as the surface of an industrial catalyst. This is important because metal catalysts are widely used in catalytic converters, fuel cells, and even to make margarine.

What makes metals tricky is that they don't have discrete energy states like molecules--rather than jumping from one specific energy level to another, electrons move between energy states in a metal in a more continuous way.

Two papers published in the journal Science this week use new algorithms to better describe what happens at the surface of metals including catalysts.

One describes the interactions between a gold surface and nitric oxide molecules excited using a laser. Older models predict that when the gas hits the gold surface it will still be vibrating. The new model predicts what actually happens: the molecule electronically couples to the gold.

The second paper looks at the interaction that cause hydrogen atoms on a copper surface to bond with one another and form hydrogen gas. It remains to be seen whether these results can be generalized, but if they can it could lead to a better understanding of the metal catalysts widely used in industrial chemistry.

Today a small group of top scientists and engineers is gathering in an auditorium on the grounds of the Army Research Laboratory in Adelphi, MD, to brainstorm new ways to solve what's becoming a major challenge for soldiers: hauling around the hundreds of batteries needed to power an ever-expanding arsenal of electronic gadgetry. Yesterday the group convened to hear an outline of the problem and learn about a lineup of technologies that could help.

U.S. Army researchers estimate that soldiers today can sometimes carry 30 pounds of batteries with them for a three-day mission. That number could increase to more than 50 pounds as soldiers are equipped with gear for networking with other soldiers on the field and back at headquarters, as well as with a growing array of sensors and robots. Weapons systems, laser range finders, night-vision gear, and other devices add to a soldier's burden.

While the participants talked about long-term solutions, such as weaving uniforms from threads that act like batteries or photovoltaics (see my story appearing online next week), nearer-term solutions, which could be in the hands of soldiers in a few years, focused on a strategy that seems to be working with car companies: hybridization. Whereas hybrid vehicles run on gasoline and batteries, soldiers will power their devices using a combination of an energy-dense fuel, such as methanol, and batteries. The methanol is great for storing a lot of energy in a small, relatively light package. But methanol-powered fuel cells have trouble quickly delivering that energy, so they aren't useful for devices that draw a lot of power, or for when a lot of devices need to be used at once. Batteries can keep up with the power demand, but they store much less energy overall. Combining the two sources of energy makes it possible to take advantage of the strengths of both.

On a typical mission, fuel cells could be used to power devices during times of low power demand, such as on the way to a fight. They could also be used to keep batteries charged, cutting down on the number needed. Once the fight begins, soldiers can switch to the batteries to power all their devices at once.