Study of Radioactive Snowballs in Superfluid Helium

引入液氦中的杂质离子可以表现为具有50-100个He原子的有效质量的单电荷实体，其被称为雪球。雪球是。因此，一个聚集体，一个氦原子的微团簇，通过电致伸缩围绕在液氦中允许的杂质核心离子周围。不仅最初注意到的氦离子，而且其他外来离子也会形成雪球。在重离子反应中极化现象的研究中所使用的方法，使我们能够通过α射线和β射线计数来研究单个的雪球，虽然雪球被认为是一个非常重要的固体实体，但仍然怀疑所有现有的证据是否都决定性地支持固体核的图像。核极化的保存在这项研究中提供了一个重要的线索，这个问题，使我们能够测试雪球的内在结构直接作为上述实验的外围问题。放射性核束从SIS加速器在GSI达姆施塔特进行了检查，并最终集中的雪球实验。强度和聚焦足以达到这一目的。雪球的寿命表明，与简单电子的相互作用有关，但与液氦中的基本激发有关。雪球的结构变得非常对称，因为它是由金属离子和氢离子组成的晶体结构。这是一个有趣的观点来理解保持核极化的核心离子被困在一个雪球。

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.