Anal Chem. 2019 Sep 3;91(17):11138-11145. doi: 10.1021/acs.analchem.9b01819. Epub 2019 Aug 19.
In the atmosphere, there are several different trajectories by which particles can nucleate ice; two of the major pathways are deposition and immersion freezing. Single particle depositional freezing has been widely studied with spectroscopic methods while immersion freezing has been predominantly studied either for particles within bulk aqueous solutions or using optical imaging of single particles. Of the few existing spectroscopic methods that monitor immersion freezing, there are limited opportunities for investigating the impact of heterogeneous chemistry on freezing. Herein, we describe a method that couples a confocal Raman spectrometer with an environmental cell to investigate single particle immersion freezing along with the capability to investigate in situ the impact of heterogeneous reactions with ozone and other trace gases on ice nucleation. This system, which has been rigorously calibrated (temperature and relative humidity) across a large dynamic range, is used to investigate low temperature water uptake and heterogeneous ice nucleation of atmospherically relevant single particles deposited on a substrate. The use of Raman spectroscopy provides important insights into the phase state and chemical composition of ice nuclei and, thus, insights into cloud formation.
在大气中，有几种不同的轨迹可以使粒子成核结冰；其中两个主要途径是沉积和浸没成冰。用光谱方法广泛研究了单颗粒沉积成冰，而浸没成冰主要是针对在大量水溶液中的颗粒或使用单个颗粒的光学成像来研究。在少数现有的监测浸没成冰的光谱方法中，对非均相化学对成冰影响的研究机会有限。在此，我们描述了一种将共焦拉曼光谱仪与环境室耦合的方法，用于研究单颗粒浸没成冰，以及原位研究臭氧和其他痕量气体与非均相反应对冰核形成的影响的能力。该系统已经过严格校准（温度和相对湿度），可在很大的动态范围内使用，用于研究沉积在基底上的大气相关单颗粒的低温水吸收和非均相冰核形成。拉曼光谱的使用提供了对冰核的相态和化学成分的重要见解，从而深入了解云的形成。
