Diveky Matus E, Roy Sandra, David Grégory, Cremer Johannes W, Signorell Ruth
Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland.
Photoacoustics. 2020 Mar 10;18:100170. doi: 10.1016/j.pacs.2020.100170. eCollection 2020 Jun.
Photoacoustic (PA) spectroscopy enjoys widespread applications across atmospheric sciences. However, experimental biases and limitations originating from environmental conditions and particle size distributions are not fully understood. Here, we combine single-particle photoacoustics with modulated Mie scattering to unravel the fundamental physical processes occurring during PA measurements on aerosols. We perform measurements on optically trapped droplets of varying sizes at different relative humidity. Our recently developed technique - photothermal single-particle spectroscopy (PSPS) - enables fundamental investigations of the interplay between the heat flux and mass flux from single aerosol particles. We find that the PA phase is more sensitive to water uptake by aerosol particles than the PA amplitude. We present results from a model of the PA phase, which sheds further light onto the dependence of the PA phase on the mass flux phenomena. The presented work provides fundamental insights into photoacoustic signal generation of aerosol particles.
光声（PA）光谱在大气科学领域有着广泛的应用。然而，源自环境条件和粒径分布的实验偏差及局限性尚未得到充分理解。在此，我们将单颗粒光声技术与调制米氏散射相结合，以揭示气溶胶光声测量过程中发生的基本物理过程。我们在不同相对湿度下对不同大小的光学捕获液滴进行测量。我们最近开发的技术——光热单颗粒光谱（PSPS）——能够对单个气溶胶颗粒的热通量和质量通量之间的相互作用进行基础研究。我们发现，与光声振幅相比，光声相位对气溶胶颗粒的吸湿更为敏感。我们给出了光声相位模型的结果，该结果进一步揭示了光声相位对质量通量现象的依赖性。本文所呈现的工作为气溶胶颗粒的光声信号产生提供了基础见解。
