Cotterell M I, Knight J W, Reid J P, Orr-Ewing A J
School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K.
J Phys Chem A. 2022 May 5;126(17):2619-2631. doi: 10.1021/acs.jpca.2c01246. Epub 2022 Apr 25.
New approaches for the sensitive and accurate quantification of aerosol optical properties are needed to improve the current understanding of the unique physical chemistry of airborne particles and to explore their roles in fields as diverse as chemical manufacturing, healthcare, and atmospheric science. We have pioneered the use of cavity ring-down spectroscopy (CRDS), with concurrent angularly resolved elastic light scattering measurements, to interrogate the optical properties of single aerosol particles levitated in optical and electrodynamic traps. This approach enables the robust quantification of optical properties such as extinction cross sections for individual particles of known size. Our measurements can now distinguish the scattering and absorption contributions to the overall light extinction, from which the real and imaginary components of the complex refractive indices can be retrieved and linked to chemical composition. In this Feature Article, we show that this innovative measurement platform enables accurate and precise optical measurements for spherical and nonspherical particles, whether nonabsorbing or absorbing at the CRDS probe wavelength. We discuss the current limitations of our approach and the key challenges in physical and atmospheric chemistry that can now be addressed by CRDS measurements for single aerosol particles levitated in controlled environments.
需要新的方法来灵敏且准确地量化气溶胶光学特性，以增进当前对空气中颗粒物独特物理化学性质的理解，并探索它们在化学制造、医疗保健和大气科学等诸多领域中的作用。我们率先使用腔衰荡光谱法（CRDS），同时进行角分辨弹性光散射测量，以研究悬浮在光学和电动阱中的单个气溶胶颗粒的光学特性。这种方法能够可靠地量化已知尺寸单个颗粒的消光截面等光学特性。我们的测量现在可以区分散射和吸收对整体光消光的贡献，从中可以获取复折射率的实部和虚部，并将其与化学成分联系起来。在这篇专题文章中，我们表明这个创新的测量平台能够对球形和非球形颗粒进行准确而精确的光学测量，无论这些颗粒在CRDS探测波长下是无吸收性还是有吸收性。我们讨论了我们方法当前的局限性以及物理和大气化学中的关键挑战，现在可以通过对悬浮在受控环境中的单个气溶胶颗粒进行CRDS测量来解决这些挑战。
