Homogeneous ice nucleation observed in single levitated micro droplets
Homogeneous ice nucleation observed in single levitated micro droplets
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在单个悬浮微滴中观察到均匀冰核
DOI：
10.1002/bbpc.19961001120
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
L. Wöste
中科院分区：
文献类型：
--
作者：
B. Krämer;M. Schwell;O. Hübner;H. Vortisch;T. Leisner;E. Rühl;H. Baumgärtel;L. Wöste
在不同的大气条件下，在一个电动保罗陷阱内的单个孤立的微小水滴的均匀冰成核率进行了测定。液滴尺寸通过氦氖激光器散射光的角度再分辨检测来测量。通过退极化率的突然变化来检测冻结过程，这是形成非球形颗粒的指示。在T =（-37.7 0. 15）° C时，均质冰成核速率JLS =（2.2 0.4）·10 8 cm-3s-1;这些数值是在云膨胀室内测量得到的，要精确得多。单粒子观测方法消除了这些成核速率测量的复杂性。结果强调的理论，一个单一的冰胚一定大小的是足以引起整个液滴冻结。在平行和垂直偏振平面中的散射强度的退偏振比Is/ Ip从冻结颗粒表现出较宽的分布与Is/ Ip= 0.3的平均值。
Homogeneous ice nucleation rates in single isolated micro droplets of water are determined under various atmospheric conditions inside an electrodynamic Paul-trap. The droplet size is measured by angle-re- solved detection of the scattered light from a Helium-Neon laser. The freezing process is detected by a sudden change of the depolarization ratio which is an indication for the formation of non spherical particles. The experimentally determined homogeneous ice nucleation rates JLS are JLS = (2.2 0.4)·10 8 cm -3 s -1 at T = (-37.2 0.15)°C and JLS = (5.6 1.0) ·10 7 cm -3 s -1 at T = (-37.7 0.15)°C. These values are much more precise as determined by measurements inside a cloud expansion chamber. The method of single particle obser- vation eliminates complications arising from these nucleation rate meas- urements. The results underline the theory that one single ice germ of certain size is sufficient to induce the freezing of the whole droplet. The depolarization ratio of the scattered intensity in the parallel and perpendicular polarization plane I s / Ip from the frozen particles exhibits a broad distribution with a mean value of I s / Ip= 0.3.