IR- und XUV-Spektroskopie an Nanopartikeln, Erzeugung und Untersuchung von atmosphärenchemisch relevanten Sytemen, Reaktionsdynamik von Säure-Base-Reaktionen in der Aerosolphase

大小从亚纳米到微米的冷分子聚集体(这里称为冰纳米粒子)在大气过程中作为气溶胶和在星际尘埃中作为反应场所发挥着重要作用。作为大气气溶胶，它们对地球以及太阳系中其他行星和卫星的气候有重大影响。这些微小的聚集体通过相变、传质过程以及化学和光化学反应，对能量平衡和这些大气的组成产生了至关重要的影响。它们通常由H2O、NH3、CH4、CO2等小分子和简单的有机分子组成。在地球上，水和冰显然是人们感兴趣的焦点，但最近备受瞩目的太空任务发现，其他简单的分子(NH3、CH4)在我们太阳系的行星和卫星的大气中也扮演着类似的角色。有关行星和卫星大气中气溶胶的新数据让科学界非常关注冷分子聚集体。例如，最近卡西尼-惠更斯的土星S月球泰坦任务证实了冷甲烷气溶胶对泰坦S天气的重要性，并类似于水冰云在地球S大气中的作用。本提议的目的是阐明几个与行星大气和星际尘埃化学相关的纯冰系统的性质，特别是多组分冰系统。目前，我们还远未对这种复杂的纳米系统进行详细的描述和理解。原因在于很难在实验室中产生和表征这种微小的敏感系统。对于尺寸小于100纳米的气溶胶颗粒尤其如此。西格诺雷尔实验室目前拥有高度专业化的仪器，用于产生和表征气溶胶冰纳米粒子，这是本提案的重点。实验室中有不同的碰撞冷却方法和各种超音速膨胀，包括从超临界介质中快速膨胀。在碰撞池中，冷聚集体是在与周围气相的热平衡中形成的，这使得它成为研究相变的独特方法。光谱方法在表征这种弱结合聚集体中起着至关重要的作用，因为它们是敏感的、非侵入性的，而且往往是唯一的遥感方法。西格诺雷尔实验室在灵敏的红外光谱方法方面拥有所需的专业知识，利用这种方法，可以在毫秒区域内以高灵敏度和时间分辨率原位研究冰粒。为了研究高频光与冷分子聚集体的相互作用，可以使用具有质量灵敏成像探测的光离子/光电子能谱仪。这项提议的主要目标是对这种微小的冰粒进行详细的光谱表征，以揭示光谱中发现的特征图案的微观来源，并为遥感提供必要的参考数据。为此，光谱性质的确定将与分子水平上的建模相结合。在过去的几年里，西格诺雷尔和他的同事们已经开发出了专门适用于处理这些冰粒的建模方法。

Cold molecular aggregates with sizes ranging from subnanometers to microns (here referred to as ice nanoparticles) play an important role as aerosols in atmospheric processes and as reactive sites in interstellar dust3. As atmospheric aerosols they have significant impact on the climate of the Earth and of other planets and moons in our solar system. These tiny aggregates critically influence the energy balance and the composition of these atmospheres, through phase transitions, mass transfer processes, and chemical and photochemical reactions. They often consist of small molecules such as H2O, NH3, CH4, CO2, and simple organic molecules. On Earth, water and its ices are the obvious focus of interest, but recent high-profile space missions have found other simple molecules (NH3, CH4) to play a similar role in the atmospheres of planets and moons of our solar system 4. New data on aerosols in atmospheres of planets and their moons have put cold molecular aggregates very much into the focus of the scientific community. For example, the recent Cassini-Huygens mission to Saturn s moon Titan has borne out the importance of cold methane aerosols for Titan s weather and the analogy to the role of water ice clouds in the Earth s atmosphere.The aim of the present proposal is to elucidate the properties of several pure and especially multi-component ice systems with relevance in planetary atmospheres and interstellar dust chemistry. Nowadays we are still far from a detailed characterization and understanding of such complex nanosystems. The reason lies in the difficulties to generate and characterize such tiny sensitive systems in the laboratory. This is in particular true for aerosol particles with sizes below 100 nm. The Signorell laboratory currently houses highly specialized instrumentation for the generation and characterization of aerosol ice nanoparticles, which is the focus of the present proposal. Different collisional cooling methods and various supersonic expansions including rapid expansion from supercritical media are available in the laboratory. In collisional cells the cold aggregates are formed in thermal equilibrium with the surrounding gas phase, which for example makes it a unique method to study phase transitions. Spectroscopic methods play a crucial role in the characterization of such weakly bound aggregates since they are sensitive, non-invasive, and are often the only methods for remote sensing. The Signorell laboratory has the required expertise in sensitive infrared spectroscopic methods with which the ice particles can be investigated in situ with high sensitivity and a time resolution in the ms region. To study the interaction of high-frequency light with cold molecular aggregates a photoion/photoelectron spectrometer with mass-sensitive imaging detection is available. The main objective of this proposal is the detailed spectroscopic characterization of such tiny ice particles to unravel the microscopic origins of the characteristic patterns found in the spectra and to provide essential reference data for remote sensing. To this end the determination of spectroscopic properties will be combined with modeling on a molecular level. During the last years, Signorell and coworkers have developed modeling methods specially adapted to the treatment of these ice particles.