Density and temperature effects on electron mobilities in gaseous butene isomers

Abstract

The density normalized mobilities μn at low electric field strengths in the low density gases fall in the order trans-2- > cis-2- > 1- > isobutene. The respective values in the saturated vapors at 297 ± 1 K were 10.7, 4.4, 3.8, and 1.84 (10 22 molecules/cm V s). The scattering cross section σ v has a Ramsauer–Townsend-like minimum at an electron energy of 0.085 eV in trans-2-butene, 0.13 eV in cis-2-butene, 0.12 eV in 1-butene, and 0.16 eV in isobutene. The mobilities in the last three isomers increase with increasing temperature (300–500 K) and field strength [Formula: see text]. Temperature and field effects were smaller in trans-2-butene. The ratio of the field effect threshold drift velocity to the speed of sound in the low density gas is 14, 19, 20, and > 50 in iso-, 1-, cis-2-, and trans-2-butene, respectively, at 297 K. The electrons are de-energized mainly by inelastic collisions. Quasilocalization occurs to a similar extent in each of the isomers at densities [Formula: see text] and temperatures near the coexistence curve. Quasilocalization is characterized by large, negative values of ΔH and ΔS, and a small value of ΔG over a small temperature range.