Experimental investigation of the collision and optical properties of (sub)µm-sized ice and ice-coated dust particles

我们建议在大范围的温度和高真空条件下，进行(亚)μm大小的水冰、覆冰二氧化硅和纯二氧化硅颗粒与冰、二氧化硅和冰/尘靶的低速碰撞实验。这些实验旨在模拟最密集和最冷的星际云中的粒子间碰撞，已经假设和观察到了凝聚作用下的颗粒生长。最重要的是，我们感兴趣的是作为颗粒大小函数的水-冰颗粒的粘合阈值，这在文献中被广泛使用，但缺乏经验数据。最重要的是，我们还打算测量这些碰撞中的电荷转移，以评估摩擦电荷是否可能是密集星际云中自由电荷载流子的来源，在密集星际云中，经典的电离源，如紫外线和宇宙射线，是无效的。我们的研究将得到松散粒子集合的红外测量的补充，通过这些测量，我们将深入了解凝结的球形冰和覆盖着冰的尘埃粒子的光学性质。要校准分子云中尘埃质量演化、化学演化和辐射能量传输的模型，需要更深入地了解小颗粒团聚体的凝聚、破碎、摩擦带电和光学性质的组合过程。

We propose to perform low-velocity impact experiments of (sub)μm-sized water ice, ice-coated silica, and pure silica particles with ice, silica, and ice/dust targets in a wide range of temperatures and under high-vacuum conditions. These experiments are intended to simulate inter-particle collisions in the densest and coldest interstellar clouds, for which grain growth by coagulation has been postulated and observed. Above all, we are interested in the sticking threshold for water-ice particles as a function of grain size, which is widely used in the literature but for which empirical data are lacking. On top of that, we also intend to measure the charge transfer in these collisions to assess whether triboelectric charging is a possible source for free charge carriers in dense interstellar clouds in which the classical sources of ionization, i.e. ultraviolet radiation and cosmic rays, are not effective. Our study will be complemented by infrared measurements of loose particle ensembles with which we will gain insight into the optical properties of coagulated spherical ice and ice-coated dust particles. A deeper understanding of the combined processes of coagulation, fragmentation, triboelectric charging, and optical properties of small particle agglomerates is required to calibrate models of the dust-mass evolution, the chemical evolution, and the radiative energy transport in molecular clouds.