Electron transport in gaseous ethene and cyclopropane: Temperature and electric field effects

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Abstract
To check whether ethene and cyclopropane display a Ramsauer–Townsend minimum in their electron momentum transfer cross sections, electron drift velocities were measured over much larger temperature ranges than previously. Ethene: 130≤T(K)≤647, 0.25≲n(1025 molecule/m3)≲3.0. Cyclopropane: 185≤T(K)≤644, 0.13≲n(1025 molecule/m3)≲18. At 294 K vd at a given E/n was independent of n up to the highest n used. In both gases vd increases linearly with E/n up to ∼0.3 Td, then tends towards saturation at ∼4 Td. In ethene vsat is ∼17 km/s, and is ∼35 km/s in cyclopropane. The value of vsat in alkanes correlates with the inverse polarizability. Ethene has a Ramsauer–Townsend minimum in its momentum transfer cross section at 0.08 eV, and cyclopropane has one at 0.07 eV.