SBIR Phase II: A Nitrogen Dioxide Detector for the Clean Troposphere

9627217 Zahniser这个小型企业创新研究第二阶段项目将建造并演示一台用于检测对流层中二氧化氮(NO2)的仪器，二氧化氮是对流层氮氧化物(NOY)最重要的成分之一。直接测量NO2对于了解决定对流层臭氧自然水平的化学过程以及评估人类影响排放的潜在影响至关重要。直接测量未受污染的对流层中的NO2的困难来自低浓度(100pptv)和其他更丰富的氮化合物的潜在干扰。这项提议将展示一种使用红外吸收的直接光谱方法，该方法使用可调谐的半导体激光光源，直接探测清洁对流层中NO2的绝对水平。拟议研究计划的一个关键组成部分是建造一个长路径、低体积的吸收池，该吸收池将具有足够的长度(~500m)以提供足够的灵敏度，同时具有最小的体积(10升)以实现快速采样和最短的仪器响应时间。使用脉冲W激光对细胞入口处的痕量物种进行调制将允许实时背景减去以进一步提高灵敏度。对已知谱线参数进行曲线拟合的自动信号处理将提供绝对浓度水平，而无需使用校准气体。由此产生的仪器将具有4ppt的NO2检测极限和100ppt的信号平均时间S。由该程序产生的仪器将用于大气化学研究人员测量除NO2之外的其他痕量气体的浓度。长程吸收池可以单独用于激光吸收系统，用于监测工业污染物、有毒废物和燃烧排放。***

9627217 Zahniser This Small Business Innovation Research Phase II project will construct and demonstrate an instrument for the detection of nitrogen dioxide (NO2), one of the most important components of nitrogen oxide species (NOy) in the troposphere. Direct measurements of NO2 are crucial for understanding the chemical processes that determine natural levels of tropospheric ozone and for assessing potential effects of human-influenced emissions. The difficulties associated with direct measurements of NO2 in the unpolluted troposphere arise from low ( 100 pptv) concentrations and the potential for interferences from other more abundant nitrogen compounds. This proposal would demonstrate a direct spectroscopic method using infrared absorption with a tunable diode laser light source which would directly detect absolute levels of NO2 in the clean troposphere. A key component of the proposed research plan is the construction of a long path length, low volume absorption cell which would have sufficient length (~500 m) to provide adequate sensitivity and yet have a minimal volume ( 10 liters) to enable rapid sampling and a minimal instrument response time. Modulation of the trace species at the cell inlet using a pulsed W laser will allow real-time background subtraction to further increase the sensitivity. Automated signal processing using curve fitting to known spectral line parameters will provide absolute concentration levels without using calibration gases. The resulting instrument will have an NO2 detection limit of 4 ppt with a signal averaging time of 100 s. The instrumentation resulting from this program will be useful for researchers in atmospheric chemistry for measuring concentrations of other trace gases in addition to NO2. The long path absorption cell would be marketable separately for incorporation into laser absorption systems for monitoring industrial pollutants, toxic wastes, and combustion emissions. ***