Physics with Radioactive Microclusters in He II

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This project aims at obtaining basic understanding on the contribution of impurities in superfluid helium.An impurity ion forms a cluster of helium atoms around itself, owing to the electrostriction exerted by the ion. The mobility of such a cluster is extremely small as compared to a bare ion, if it exists at all, or a neutral atom.The specific features of the research here is to use radioactive impurities to enable detection of various kinds of impurities.From out studies, it has become clear that such impurities are produced in superfluid helium by implantation of high-speed radioactive nuclear beams, and the charged impurities can be transported in the electric field. Thus trapping of such impurities is realizable.Nuclear polarization of impurities encapsulated in snowball is preserved. If the electric field is quite strong ions may migrate free from the surrounding cluster shell and the polarization seems to be lost. Neutrals have no polarization conserved.Based on the facts, gathered from our unique research, a new field of physics branching on nuclear physics and condensed-matter physics will be cultivated by using a radioactive nuclear beams from the SIS and FRS system of the GSI Darmstadt in cooperation with GSI and other institutions. The nuclear structure and spectroscopy of radioactive nuclei far from the stability line stressed on the control of nuclear spin is in the former field. Structure of clusters and the interaction of impurities with the bulk superfluid helium belongs to the latter field. It can be emphasized that the detection efficiency of clusters "snowballs" became by many orders of magnitude more sensitive by the detection methods developed here.The trapping of radioactive nuclei is also an interesting subject and this will be applied in a wide field of nuclear and particle physics.