MULTIPASS OPTICAL-ABSORPTION SPECTROSCOPY - A FAST-SCANNING LASER SPECTROMETER FOR THE IN-SITU DETERMINATION OF ATMOSPHERIC TRACE-GAS COMPONENTS, IN PARTICULAR OH

The optical design of an absorption spectrometer for in situ measureme nts of atmospheric trace gases is reported. The light source is a rapi dly tuned and power-stabilized dye-ring laser, which is frequency doub led by an intracavity BBO crystal. The second harmonic and the fundame ntal are used simultaneously for measurement of OH, SO2, CH2O, and nap hthalene in the UV and of NO2 in the visible. The 1.2-km absorption pa th is folded within a 6-m White-cell-type multiple-reflection system w ith an open-path setup. The absorption sensitivity of the spectrometer is better than 1 part in 10(-5) under tropospheric conditions (integr ation time 1 min., signal-to-noise ratio 1). (C) 1996 Optical Society of America