Study of Radioactive Snowballs in Superfluid Helium

引入液氦的杂质离子可能表现为有效质量为50-100个He原子的单电荷实体，这被称为雪球。雪球是。因此，一个聚集体，一个氦原子的微团簇，通过电伸缩围绕一个杂质核离子在液氦中被接纳。不仅是最初注意到的氦离子，其他外来离子也会形成雪球。在重离子反应极化现象的研究中所使用的方法使我们对通过在这里发展的α射线和β射线计数来接近单个雪球产生了新的兴趣。虽然雪球被认为是一个非常重要的固体实体，但是否所有现有的证据都决定性地支持固体核的观点，仍然存在疑问。本研究中原子核极化的保存为这一问题提供了重要线索，使我们能够直接测试雪球的内在结构，从而解决上述实验的外围问题。对来自达姆施塔特GSI SIS加速器的放射性核束进行了检查，并最终集中进行了雪球实验。影片的强度和聚焦度足以达到这个目的。雪球的寿命表明，雪球的相互作用不是与简单电子的相互作用，而是与液氦中的基本激发的相互作用。与金属离子和氢离子组成的晶体结构相比，雪球的结构明显具有高度对称性。这对于理解如何在被困在雪球中的核心离子中维持核极化是一个有趣的观点。

Impurity ions introduced in liquid helium may behave as singly charged entities with effective mass of 50-100 He atoms, which are referred to as snowballs. A snowball is. therefore, an aggregate, a micro-cluster of helium atoms by means of electrostriction around an impurity core ion admitted in liquid helium. not only helium ions as first noticed but also other alien ions do form snowballs. The method used in the of study of polarization phenomena in heavy ion reactions enabled us to conceive renewed interests to approach individual snowballs though alpha- and beta-ray countings, which have been developed here.While the snowball has been thought of a highly paramount solid entity, there are still doubt whether all the existing evidences do decisively favor the picture of a solid core. The preservation of nuclear polarization in this research provided with an important clue to this issue, enabling us to test the inherent structure of snowballs directly as to peripheral problems of the above experiment.The radioactive nuclear beams from the SIS accelerator at GSI Darmstadt was examined and finally focussed for of snowball experiments. The intensity and focussing were enough for that purpose.The lifetime obtained for snowballs indicates the interaction responsible is not that with simple electrons but with basic excitations in liquid helium.The structure of snowball became clearly highly symmetric, as it was compared with the crystal structure composed of metal ion and hydrogen ions. This is an interesting point of view for understanding of maintaining nuclear polarization in the core ion trapped in a snowball.