Radical Measurements

Research Group Dr. Hartwig Harder

Why are we interested in radicals? Radicals, having an unpaired electron, are highly reactive. This makes them the driving molecules in air chemistry. They cleanse the atmosphere, are responsible for the formation of ozone (O₃) and can also initiate aerosol formation.

One of the prime radicals for air chemistry is the hydroxyl radical, OH. Simple in structure, it is one of the most reactive molecules in the atmosphere. It is mainly formed by water molecules, ozone and sunlight, which are available almost everywhere. This ubiquitous production source makes it the most important oxidizing molecule in the atmosphere. A close chemical relative, the hydroperoxyl radical, HO₂, is a major source of tropospheric ozone. It reacts with the NO radical to form NO₂, which is then photolyzed, producing ozone. In addition, OH and HO₂, together called HO_x, play a role in the production of aerosols through the formation of low volatility compounds like organic acids or sulfuric and nitric acid. Thus OH and HO₂ both initiate and participate in almost all of the atmosphere's complex chemical pathways.