Searches for fractional electric charge on niobium samples exposed to liquid helium

Abstract

Levitation measurements at room temperature described in a previous paper did not confirm the apparent fractional electric charges reported by the Stanford Group for niobium samples at liquid helium temperature. To simulate possible effects of a low-temperature environment, both niobium and steel samples have been exposed to liquid helium for periods of typically 48 h, both with and without the assistance of electric fields to extract possible fractionally charged ions. Subsequent levitation tests show no indication of fractional charge. With some additional assumptions regarding ionic mobility and surface energy, an upper limit ∼10 −2 fractional charges/g is inferred for the liquid helium itself.