A new instrument for the measurement of atmospheric nitrous acid (HONO) and hydroxyl radicals (OH) has been developed using laser photofragmentation (LP) of HONO at 355 nm after expansion into a low-pressure cell, followed by resonant laser-induced fluorescence (LIF) of the resulting OH radical fragment at 308 nm similar to the fluorescence assay by gas expansion technique (FAGE). The LP/LIF instrument is calibrated by determining the photofragmentation efficiency of HONO and calibrating the instrument sensitivity for detection of the OH fragment. In this method, a known concentration of OH from the photo-dissociation of water vapor is titrated with nitric oxide to produce a known concentration of HONO. Measurement of the concentration of the OH radical fragment relative to the concentration of HONO provides a measurement of the photofragmentation efficiency. The LP/LIF instrument has demonstrated a 1σ detection limit for HONO of 9 ppt for a 10 min integration time. Ambient measurements of HONO and OH from a forested environment and an urban setting are presented along with indoor measurements to demonstrate the performance of the instrument.

中文翻译：

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用于检测大气中亚硝酸和羟基自由基的激光光碎裂激光诱导荧光仪的研制

已经开发了一种用于测量大气亚硝酸 (HONO) 和羟基自由基 (OH) 的新仪器，使用 HONO 在 355 nm 处的激光光碎 (LP) 在扩展到低压池后，然后进行共振激光诱导荧光。所得 OH 自由基片段在 308 nm 处的 LIF)，类似于通过气体膨胀技术 (FAGE) 进行的荧光测定。LP/LIF 仪器通过确定 HONO 的光碎效率和校准仪器灵敏度来校准以检测 OH 碎片。在该方法中，已知浓度的来自水蒸气光解的 OH 用一氧化氮滴定以产生已知浓度的 HONO。相对于 HONO 浓度的 OH 自由基碎片浓度的测量提供了光碎效率的测量。LP/LIF 仪器已经证明了 1HONO 的σ检测限为 9 ppt，积分时间为 10 分钟。展示了森林环境和城市环境中 HONO 和 OH 的环境测量值以及室内测量值，以展示仪器的性能。