Abstract

Near-visible absorption lines of ambient H₂O vapor and normal and heavy isotopes of O₂ have been measured over atmospheric paths of up to 0.46 km by using two wavelength-modulated, line-locked AlGaAs laser sources with a retroreflector–telescope system. The absolute signal levels agree with theoretical calculations for the O₂ isotopes to within 2%, which is similar to the accuracy with which the column densities were known. Measurements of ¹⁶O₂ linewidths and line strengths were made, and they agree with literature values to within experimental error. The detection sensitivity for ¹⁶O¹⁸O was found to be 0.1 part in 10⁶ atm. km, corresponding to an absorbance sensitivity of 1 × 10⁻⁵. It is concluded that atmospheric trace-gas sensing will be feasible with this apparatus over distances of several kilometers and at levels under 1 part in 10⁶.

© 1993 Optical Society of America

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