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

小行星9627217 这个小企业创新研究第二阶段项目将构建和演示一种用于检测二氧化氮（NO2）的仪器，二氧化氮是对流层中氮氧化物（NOy）的最重要组成部分之一。NO2的直接测量对于了解决定对流层臭氧自然水平的化学过程和评估人为排放的潜在影响至关重要。在未污染的对流层中直接测量NO2的困难来自低浓度（100 pptv）和来自其他更丰富的氮化合物的干扰的可能性。该提案将展示一种使用红外吸收的直接光谱方法，该方法使用可调谐二极管激光光源，可直接检测清洁对流层中NO2的绝对水平。拟议的研究计划的一个关键组成部分是建设一个长的路径长度，低容量的吸收池，将有足够的长度（~500米），以提供足够的灵敏度，但有一个最小的体积（10升），使快速采样和最小的仪器响应时间。使用脉冲W激光器在池入口处调制痕量物质将允许实时背景扣除以进一步增加灵敏度。使用曲线拟合已知谱线参数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。所得仪器的NO2检测限为4 ppt，信号平均时间为100 s。 该计划产生的仪器将有助于 大气化学研究人员测量除NO2外的其他痕量气体的浓度。 长光程吸收池可以单独销售，用于并入激光吸收系统，以监测工业污染物、有毒废物和燃烧排放物。 ***

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. ***