Water diffusion measurements of single charged aerosols using H2O/D2O isotope exchange and Raman spectroscopy in an electrodynamic balance†,Physical Chemistry Chemical Physics

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Water diffusion measurements of single charged aerosols using H2O/D2O isotope exchange and Raman spectroscopy in an electrodynamic balance†
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2019-06-11 00:00:00 , DOI: 10.1039/c8cp07052k
Katherine A. Nadler _{1,

2,

3,

4} , Pyeongeun Kim _{1,

2,

3,

4} , Dao-Ling Huang _{1,

2,

3,

4} , Wei Xiong _{1,

2,

3,

4} , Robert E. Continetti _{1,

2,

3,

4}

Affiliation

Sea spray aerosols contain a large array of organic compounds that contribute to high viscosities at low relative humidity and temperature thereby slowing translational diffusion of water. The Stokes–Einstein equation describes how viscosity is inversely correlated with the translational diffusion coefficient of the diffusing species. However, recent studies indicate that the Stokes–Einstein equation breaks down at high viscosities achieved in the particle phase (>10¹² Pa s), underestimating the predicted water diffusion coefficient by orders of magnitude and revealing the need for directly studying the diffusion of water in single aerosols. A new method is reported for measuring the water diffusion coefficient in single suspended charged sucrose–water and citric acid (CA)–water microdroplets in the 30–60 micron diameter range. The translational water diffusion coefficient is quantified using the H₂O/D₂O isotope exchange technique between 26 and 54% relative humidity (RH) for sucrose and 7 and 25% RH for CA using a recently developed mobile electrodynamic balance apparatus. The results are in good agreement with the literature, particularly the Vignes-type parameterization from experiments using isotope exchange and optical tweezers. Below 15% RH, CA droplets show incomplete H₂O/D₂O exchange. This mobile electrodynamic balance will allow future studies of atmospherically relevant chemical systems, including field studies.

中文翻译：

在电平衡中使用H ₂ O / D ₂ O同位素交换和拉曼光谱法测量单电荷气溶胶的水扩散†

海水喷雾气溶胶包含大量有机化合物，这些有机化合物可在较低的相对湿度和温度下提高粘度，从而减缓水的平移扩散。斯托克斯-爱因斯坦方程描述了粘度与扩散物质的平移扩散系数成反比的关系。但是，最近的研究表明，斯托克斯-爱因斯坦方程在粒子相达到的高粘度（> 10 ¹²Pa s），将预测的水扩散系数低估了几个数量级，并揭示了直接研究单个气溶胶中水扩散的必要性。据报道，有一种新方法可以测量直径在30至60微米范围内的单个悬浮带电蔗糖-水和柠檬酸（CA）-水微滴中的水扩散系数。使用H ₂ O / D ₂量化平移水扩散系数使用最新开发的移动式电动平衡装置，蔗糖的相对湿度（RH）在26％至54％相对湿度下，CA相对湿度在7％至25％之间的O同位素交换技术。结果与文献非常吻合，特别是使用同位素交换和光镊的实验中的Vignes型参数化。相对湿度低于15％时，CA液滴显示出不完全的H ₂ O / D ₂ O交换。这种移动的电动平衡将允许将来对大气相关的化学系统进行研究，包括现场研究。

更新日期：2019-06-11

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