Long-Path Intracavity Laser Spectrometer for the Measurementof Atmospheric Trace Gases

在可见光到近紫外波段有许多重要的大气微量气体的吸收谱线。这些气体的吸收截面是温和的，但它们极低的浓度（有些低于万亿分之一的水平）使它们难以测量。第一阶段的工作将研究一种提高腔内激光吸收光谱灵敏度的技术，并应用于大气中微量气体的探测和测量。该技术将多通吸收电池置于染料激光器的谐振腔内。使用腔内多通池，光学吸收光路长度可以比典型的实验系统值增加十到三十倍。腔内激光光谱学可以将灵敏度提高到现有技术的10倍或更多。第一阶段研究的总体目标是展示和探索具有腔内长程多通吸收细胞的可调谐染料激光器的行为。本文将评估这种激光系统在测量大气弱吸收气体问题上的适用性。基于该系统的大气痕量气体测量仪器将具有现代大气化学研究所需要的许多特性。这些特性包括：高灵敏度，快速响应，点测量能力和坚固耐用。

There are numerous important atmospheric trace gases with absorption lines in the visible to near ultraviolet. The absorption cross sections for these gases are moderate, but their extremely low concentrations (some below part-per- trillion levels) make them difficult to measure. The Phase I effort will investigate a technique for increasing the sensitivity of intracavity laser absorption spectroscopy, with application to the detection and measurement of trace gases in the atmosphere. The technique places a multipass absorption cell within the resonant cavity of a dye laser. With an intracavity multipass cell, the optical absorption pathlength can be increased by a factor of ten to thirty over the typical values of experimental systems. Intracavity laser spectroscopy may increase sentivity by a factor of ten or more over the previous state of the art. The general goal for Phase I research is to demonstrate and explore the behavior of a tunable dye laser that has an intracavity long-path multi-pass absorption cell. The applicability of such a laser system to the problem, of measuring weakly absorbing atmospheric gases will be evaluated. An atmospheric trace gas measurement instrument based on this system would have many of the properties desired in modern atmospheric chemistry research. These properties include: high sensitivity, fast response, point measurement capability and ruggedness.