SNOWBALLS OF RADIOACTIVE IONS - NUCLEAR-SPIN POLARIZATION OF CORE IONS

Short-lived ions B-12 (beta-radioactive, T-1/2 = 20.3 ms) sustaining n uclear spin polarization were introduced into superfluid helium at 1.7 K. It was found that the B-12 ions were transported as charged entiti es under a static electric field and that the nuclear polarization was maintained throughout the lifetime of B-12 nuclei. Polarization of B- 12 was determined through beta-NMR method. ''Snowball'', a singly char ged microcluster of helium atoms formed around an impurity ion, is res ponsible for the behaviour and thus constitutes a suitable environment for preserving nuclear polarization of the core ions B-12. In a separ ate experiment snowballs were produced by implanting Li-8 (T-1/2 = 830 ms) into liquid helium and detected by means of alpha particles from the core ions to guarantee that the snowballs survive longer than the lifetime of B-12.