Creation and Annihilation of Microclusters with an Impurity Core Ion in Low-Temperature Condensed Matter

点击翻译按钮获取中文摘要

Impurity ions introduced in superfluid helium form charged aggregations called snowballs. They are considered microclusters tightened through electrostriction.In this research project, such snowballs are created through introduction of radioactive ions produced in high-energy heavy-ion collisions. Thus short-lived ions, such as ^<12>B (halflife 20,4 ms) and ^8Li (halflife 842 ms) are used as impurity core ions. The processes of creation and annihilation of snowballs are studied employing novel methods of detecting beta rays and alpha particles from the nuclei of the core ions.The experimental studies were proceeded along two lines, 1) nucleation probability has been determined ; the ratio of number of snowballs formed to number of impinging ions into superfluid helium, has been measured by observing the numbers of decay beta rays from ^<12>B.2) The preservation of nuclear polarization in impurity core ions is a good probe to seek into the phase of helium atoms as directly neighboring the impurity ions in snowballs. Our result reflects that the structure of a snowball is most probably of solid entity and the atomic structure is highly symmetric, as often presumed, the icosahedral orientation may be one of the candidates for the atomic configuration around the core ion.The experimental studies are carried out at RCNP,Osaka University and partly at RIKEN using the cyclotron systems.