Direct Measurements of the Optical Cross Sections and Refractive Indices of Individual Volatile and Hygroscopic Aerosol Particles
Direct Measurements of the Optical Cross Sections and Refractive Indices of Individual Volatile and Hygroscopic Aerosol Particles
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DOI：
10.1021/acs.jpca.5b00435
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发表时间：
2015-06-04
影响因子：
2.9
通讯作者：
Reid, J. P.
中科院分区：
文献类型：
--
作者：
Mason, B. J.;Cotterell, M. I.;Reid, J. P.
我们提出的测量过程中的挥发性组分或吸湿增长的单个粒子陷阱形成的贝塞尔光束和腔衰荡光谱的组合的挥发性组分或吸湿增长的单个气溶胶粒子（跨越700-2500 nm的半径）的消光截面的演变。对于1，2，6-己三醇、聚乙二醇400和甘油的单组分有机气溶胶液滴，有机组分的缓慢蒸发（在1000至101300 s的时间尺度上）导致随时间变化的尺寸和消光截面，其可用于估计液滴的折射率。测量二元含水无机气溶胶液滴含有一种无机溶质硫酸氢铵，硫酸铵，硝酸钠，或氯化钠（在1000至15 000 s的时间尺度）的条件下，不断变化的相对湿度表明，消光截面测量是一致的预期从公认的模型的变化液滴的折射率与吸湿增长。此外，我们使用这些系统建立一个实验协议，为未来的单粒子消光测量。讨论了绘制单个颗粒在延长的时间范围内（伴随着吸湿循环或成分蒸发）不断变化的消光横截面的优点。
We present measurements of the evolving extinction cross sections of individual aerosol particles (spanning 700-2500 nm in radius) during the evaporation of volatile components or hygroscopic growth using a combination of a single particle trap formed from a Bessel light beam and Cavity ring-down spectroscopy. For single component organic aerosol droplets of 1,2,6-hexanetriol, polyethylene glycol 400, and glycerol, the slow evaporation of the organic component (over time scales of 1000 to 101300 s) leads to a time-varying size and extinction cross section that can be used to estimate the refractive index of the droplet. Measurements on binary aqueous inorganic aerosol droplets containing one of the inorganic solutes ammonium bisulfate, ammonium sulfate, sodium nitrate, or sodium chloride (over time scales of 1000 to 15 000 s) under conditions of changing relative humidity show that extinction cross-section measurements are consistent with expectations from accepted models for the variation in droplet refractive index with hygroscopic growth. In addition, we use these systems to establish an experimental protocol for future single particle extinction measurements. The advantages of mapping out the evolving light extinction cross-section of an individual particle over extended time frames accompanied by hygroscopic cycling or component evaporation are discussed.