Earth's atmosphere is a complicated dance of molecules. The chemical output of plants, animals and human industry rise into the air and pair off in sequences of chemical reactions. Such processes help maintain the atmosphere's chemical balance; for example, some break down pollutants emitted from the burning of fossil fuels. Understanding exactly how these reactions proceed is critical for predicting how the atmosphere will respond to environmental changes, but some of the steps of this dance are so quick that all of the molecules involved haven't been measured in the wild.

A University of Pennsylvania team has now observed one of these rapid atmospheric reactions in the lab. They identify an important intermediate molecule and track its transformation to hydroxyl radicals, also demonstrating the amount of energy necessary for the reaction to take place.

Their findings help explain how the atmosphere maintains its reserves of hydroxyl radicals, highly reactive molecules that are called the "atmosphere's detergent."

The study was led by Marsha Lester, professor of chemistry in Penn's School of Arts & Sciences, along with members of her lab: graduate student Fang Liu and postdoctoral researcher Joseph Beames. They collaborated with Andrew Petit, also a postdoctoral researcher in the Department of Chemistry, and Anne McCoy, professor of chemistry at The Ohio State University.

Their work was published in Science.