Experimental evidence for the existence of a Ramsauer–Townsend minimum in liquid CH4 and Ar (Kr and Xe) and in gaseous C2H6 and C3H8

Abstract

Experimental evidence for the existence of a Ramsauer–Townsend minimum in the electron scattering cross section for liquid CH4 and liquid Ar (Kr and Xe) is presented and discussed. On the basis of evidence obtained from three sources: (i) comparisons of thermal electron mobilities in gases with those in liquids, (ii) changes in the electron mobility with gas density at high and very high gas pressures, and (iii) the dependence of the electron mobility on temperature for liquids whose V0, the energy of the electron state in the liquid, is ≤0 eV, it is concluded that a Ramsauer–Townsend minimum is exhibited by the electron scattering cross section for CH4, Ar (Kr and Xe) at all densities from a dilute gas to the liquid and that this minimum is shifted to lower energies (closer to thermal) with increasing density.Additionally, it has been found that a Ramsauer–Townsend-type behavior is exhibited by gaseous ethane (C2H6) and propane (C3H8) with the cross section minimum located at lower energies than for methane (CH4). For these latter molecules the measured mean scattering cross sections at thermal energies are comparable with the geometric cross sections.