Experimental Investigations of the Contact Freezing Properties of Mineral Particles Using Optical Tweezers

美国国家科学基金会化学部的环境化学科学项目支持Ryan Sullivan教授的研究，他将使用光镊确定与大气相关的矿物颗粒成分的接触冷冻特性。沙利文教授和他的学生将确定各种类型的矿物尘埃颗粒通过接触冻结催化过冷液滴自发异质冻结的能力。液滴将悬浮在一个聚焦激光束使用制冷光学镊子系统。检索的拉曼光谱将提供液滴的关键信息？冷冻发生之前和冷冻发生时的物理和化学状态。在冻结之前发生的尘埃颗粒-液滴碰撞的数量将被明确地知道，并且接触冻结也将与浸没冻结机制区分开。这项研究将有助于解决有关大气中接触冻结普遍存在的长期悬而未决的问题，及其对改变云的性质和诱导降水的潜在重要性。拟议的研究将有助于填补有关无处不在的分子的基本相变的重要知识空白我们的环境：水。这些结果将影响从物理化学到地球化学和大气科学的广泛领域，并增加我们对气溶胶-云-气候相互作用的理解。这些发现对于改进目前用于天气预报和全球气候模型的过时的非均质冰成核描述尤为重要。该项目将为学生提供宝贵的经验，在新的使用光镊研究异质冰成核的第一次。我们与布里斯托大学科学家的国际合作将为我们的学生提供独特的机会，让他们接受专家培训，使用光学镊子进行大气气溶胶颗粒研究。该项目将在一个具有重大社会意义的研究领域为学生提供培训机会。

The Environmental Chemical Sciences Program in the Chemistry Division at the National Science Foundation supports the research of Professor Ryan Sullivan at Carnegie-Mellon who will determine the contact freezing properties of atmospherically relevant mineral particle compositions using optical tweezers. Professor Sullivan and his students will determine the ability of various types of mineral dust particles to catalyze the spontaneous heterogeneous freezing of supercooled droplets through contact freezing. The droplets will be suspended in a focus laser beam using a refrigerated optical tweezers system. The retrieved Raman spectrum will provide key information on the droplet?s physical and chemical state just prior to and when freezing occurs. The number of dust particle-droplet collisions that occur before freezing will be explicitly known, and contact freezing will also be discriminated from immersion freezing mechanisms. This research will help to resolve long outstanding questions regarding the prevalence of contact freezing in the atmosphere, and its potential importance for modifying cloud properties and inducing precipitation.The proposed research will help fill an important knowledge gap regarding a fundamental phase transition of a ubiquitous molecule in our environment: water. The results will impact a wide range of fields from physical chemistry to biogeochemistry and atmospheric science, and increase our understanding of aerosols-cloud-climate interactions. The findings will be particularly important for improving the outdated descriptions of heterogeneous ice nucleation currently used in weather forecast and global climate models. The project will provide students with valuable experience in the novel use of optical tweezers to study heterogeneous ice nucleation for the first time. Our international collaboration with scientists at the University of Bristol will afford our students with the unique opportunity to be trained by experts in the use of optical tweezers for atmospheric aerosol particle research. The project will provide training opportunities for students in a research area of great societal importance.