Abstract: | The detection of atmospheric OH radicals by laser long path absorption spectroscopy is described. This technique is specific to OH and easily calibrated. In various field measurements from below the detection limit (5*105/cm3) up to 8.7* 106 OH radicals/cm1 have been observed. Measurements of meteorologic parameters and mixing ratios of other trace gases simultaneously with OH allow comparison of observed OH levels with reaction kinetic model calculations. |