Study of Radioactive Snowballs in Superfluid Helium

在液氦中引入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，称为雪球。雪球就是。因此，氦原子的聚集体是通过电致伸缩的方式围绕在液态氦中允许的杂质核心离子周围的。不仅如第一次注意到的那样，氦离子，而且其他外星离子也会形成雪球。在研究重离子反应中的极化现象时使用的方法使我们重新产生了兴趣，通过这里开发的α和β射线计数来接近单个雪球。虽然雪球一直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确实有利于固体核的图景，仍然存在疑问。本研究中核极化的保存为这一问题提供了重要线索，使我们能够针对上述实验的外围问题直接测试雪球的固有结构。对来自GSI Darmstadt的SIS加速器的放射性核束进行了检查，并最终聚焦于雪球实验。雪球的寿命表明，这种相互作用不是与简单电子的相互作用，而是与液体氦中的基本激发相互作用。与金属离子和氢离子组成的晶体结构相比，雪球的结构变得明显高度对称。这对于理解被困在雪球中的核心离子保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.