Mobility of thermal cations in low density alkane gases

Mobilities µ of thermal cations were measured in gases of six linear n-alkanes, ethane to n-decane, and in i-butane and neo-pentane, as functions of density n and temperature T. The low density limit was reached where nµ and the temperature coefficient at constant n, (dnµ,/dT)n, were constant. At all temperatures the average momentum transfer cross sections σave equalled (1.2 ± 0.4) times the cross sections expected from simple polarization. At high temperature σave might be approaching a hard sphere limit.