Quasi-particle scattering with polarized nuclei on ion cluster in liquid ^3He

点击翻译按钮获取中文摘要

Ion in liquid ^3He has a different structure depending on its sign of the charge. A positive ion, so called a "snowball", has localized ^3He spins on the surface. On the contrary a negative ion is a bubble in which an electron is trapped. Ion mobility at low temperatures below 100 mK is determined by scattering with Landau quasi-particles, hence the situation resembles an impurity scattering in metals. In the case of positive ion, the exchange scattering of localized ^3He spins on the ion surface with quasi particles seems to play an important role. To investigate such an effect, positive ion mobility in normal liquid. ^3He has been measured as a function of external magnetic fields up to 15 T at temperatures down to 3 mK. It does depend on the magnetic field at high pressures above 20 bars. Especially at 3.2 mK, it has a pressure dependent small and broad peak followed by a drastic decrease of about 30 % with increasing the field. On the other hand, at 20 mK, a monotonous decrease with increasing the magnetic field has been observed in the same pressure region. In contrast negative ion mobility at 29 bar is found to be independent of both temperature and magnetic field. These facts indicate that there exists an exchange interaction between ^3He quasi-particle and "snowball". However the results are too complicated for us to clarify the mechanism at present. Further systematic experiments should be made in the wide range of parameters, and a new theoretical treatment is eagerly desired to understand the positive ion mobility under high magnetic fields.