Paramagnetic Attraction of Impurity-Helium Solids

A small permanent magnet was used to attract impurity-helium solid samples composed of hydrogen, deuterium, and nitrogen radicals. The magnetic field gradient was sufficiently strong to lift each of the impurity-helium solids while submerged in superfluid helium, but only strong enough to lift one of four samples through the liquid surface. This suggests ranges of local atomic radical concentrations that partially agree with previous ESR measurements. The attractive paramagnetic force is strong enough to be useful as a trap for the formation of a pure hydrogen impurity-helium solid, for use in radical concentration measurements and for sorting and moving impurity-helium solids.