| The vital role of experimental probes in expanding the horizons of our knowledge of atmospheric chemistry has long been recognized. Application of the growing constellation of spectroscopic techniques to the study of trace gas photochemistry has constituted a new paradigm and contributed in many ways to our understanding of the troposphere. We present a novel technique, Long-Path Diode Array Differential Optical Absorption Spectroscopy (LPDA DOAS), to monitor trace gases in the troposphere. The technique is based on the multiplex advantage of the diode array and the principle of a 'differential' optical absorption cross-section. It enjoys the distinction of being an ambient measurement and hence avoids the pitfalls arising due to sampling biases and wall effects. The use of a diode array permits the dynamic and simultaneous acquisition of constituent spectra, rapid signal averaging, and enhanced dynamic range and signal-to-noise ratio. We show that the technique is sensitive, rapid, and lends itself to a straightforward analysis of species concentration and related photochemical parameters. Furthermore, the use of long optical paths makes this technique useful in relatively clean environments and allows for intercomparison with computer models of the troposphere. |
