Ion and electron mobilities in cryogenic liquids: Argon, nitrogen, methane, and ethane

Abstract

Ion mobilities at low fields have been measured over the entire liquid range in argon, nitrogen, and methane. Gas-phase values for argon and nitrogen are also given. Comparison of the ratio of electron to ion mobilities confirmed that the electron remains nearly free in argon and methane liquids but is an anion in liquid nitrogen. At T≲116 K, the product of viscosity and either cation or anion mobility is constant in liquid nitrogen under its vapor pressure. At T>118 K, an abrupt destabilization of the anion in the low density liquid occurs; the breakdown strength of nitrogen should sharply decrease. The utility of breakdown studies in liquid ethane and propane in bridging studies of cryogenic inorganic liquids to studies of normal liquid hydrocarbons is discussed.