Energetics and possible formation and decay mechanisms of vortices in helium nanodroplets
Energetics and possible formation and decay mechanisms of vortices in helium nanodroplets
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DOI：
10.1103/physrevb.68.224520
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发表时间：
2003-12-01
影响因子：
3.7
通讯作者：
Schmied, R
中科院分区：
文献类型：
--
作者：
Lehmann, KK;Schmied, R
尽管漩涡在块状超流氦中不可避免地存在，但迄今为止还没有在氦纳米液滴中观察到它们。研究了氦纳米液滴直涡态和弯曲涡态的能量和角动量随液滴尺寸的变化规律。对于许多实验尺寸范围内的液滴，发现在重溶质拾取过程中，相当一部分事件积累了足够的能量和角动量，形成了一条直线涡旋线。弯曲的涡旋线存在到几乎为零的角动量和能量，因此原则上可以在几乎任何碰撞中形成。此外，在膨胀冷却过程中，较小液滴的聚合也可以沉积足够的角动量来形成涡旋线。尽管能量很高，但大多数涡旋预计在氦纳米液滴的最终温度(0.38K)下是稳定的，这是因为缺乏同时守恒能量和角动量的衰变通道。
Though vortices are an unavoidable presence in bulk superfluid helium, they have not been observed to date in helium nanodroplets. The energy and angular momentum of both straight and curved vortex states of a helium nanodroplet are examined as a function of droplet size. For droplets in the size range of many experiments, it is found that during the pickup of heavy solutes, a significant fraction of events deposit sufficient energy and angular momentum to form a straight vortex line. Curved vortex lines exist down to nearly zero angular momentum and energy, and thus could in principle form in almost any collision. Further, the coalescence of smaller droplets during the cooling by expansion could also deposit sufficient angular momentum to form vortex lines. Despite their high energy, most vortices are predicted to be stable at the final temperature (0.38 K) of helium nanodroplets due to lack of decay channels that conserve both energy and angular momentum.