Ion/atom trap with use of superfluid helium

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Alian ions in supefluid helium form a micro-clusters of helium atoms due to electrostriction. The structure of the cluster is thought to be highly symmetric and thus spin orientation of the core ion may be preserved. This feature is quite attractive for application to spectroscopic studies of unstable nuclei far from stability. We investigated feasibility and applicability of superfulid helium as an ion-trap.The preservation of spin polarization was ensured by using spin-polarized 12B beams. The formation probability of the micro-cluster in which the implanted ion preserves its charge was as high as 20 % of the implated ions. Spatial manupilation of the cluster under the electrostatic field was performed. Next step is a boostup of polarization by using laser optical pumping. Dificulties of the pumping have been investigated.As an application to the spectroscopic studies, beta-delayd neutron dacay of 17B has been observed. By measureing the beta-ray asymmetry in coincidence with the decaying neutrons, it was demonstrated that individual spin-parity assignment for the excited stated of 17C was possible. This new method is very promissing for the studies of exotic nuclei. Combination with the helium ion trap may serve as a new tool for the systematic studies of exotic nuclei.