Moridnejad Ali, Preston Thomas C, Krieger Ulrich K
Department of Atmospheric and Oceanic Sciences and Department of Chemistry, McGill University , 805 Sherbrooke Street West, Montreal, QC, Canada H3A 0B9.
Institute for Atmospheric and Climate Science, ETH Zurich , Zurich, Switzerland.
J Phys Chem A. 2017 Oct 26;121(42):8176-8184. doi: 10.1021/acs.jpca.7b06774. Epub 2017 Oct 16.
Morphology-dependent resonances (MDRs) can serve as a sensitive probe of the size and composition of microspheres. While the utilization of MDRs to characterize homogeneous spheres is now routine, analysis of spherical particles with more complicated refractive index profiles can be extremely difficult and time consuming. In ultraviscous and glassy aerosol particles, the concentration profile of water during sorption often contains a sharp front that propagates from the particle surface to the particle center over time. Here we show that the MDR positions associated with this type of concentration profile closely match those of a spherical core-shell profile. Due to the similarities, a core-shell model can be used to simplify the analysis of MDR positions that are observed during water uptake by high-viscosity aerosol particles. We examined the applicability and limitations of this core-shell model in the tracking of water sorption by single particles. Overall, the core-shell model allows for the radial position of a sharp diffusion front to be readily found using MDR positions observed during water sorption, making the analysis of light-scattering measurements much faster and less error prone than previously used fitting schemes. Additionally, methods for calculating MDRs in spherical core-shell particles are also discussed.
形态依赖共振（MDRs）可作为微球尺寸和组成的灵敏探针。虽然利用MDRs表征均匀球体现已成为常规操作，但分析具有更复杂折射率分布的球形颗粒可能极其困难且耗时。在超粘性和玻璃态气溶胶颗粒中，吸附过程中水的浓度分布通常包含一个尖锐前沿，该前沿会随着时间从颗粒表面向颗粒中心传播。在此我们表明，与这种浓度分布类型相关的MDR位置与球形核壳分布的位置紧密匹配。由于存在这些相似性，核壳模型可用于简化对高粘性气溶胶颗粒吸水过程中观察到的MDR位置的分析。我们研究了该核壳模型在追踪单个颗粒吸水情况时的适用性和局限性。总体而言，核壳模型使得利用吸水过程中观察到的MDR位置能够轻松找到尖锐扩散前沿的径向位置，与先前使用的拟合方案相比，大大加快了光散射测量的分析速度且降低了出错几率。此外，还讨论了计算球形核壳颗粒中MDRs的方法。
