Energy of the excess electron in methane and ethane near the critical point

Field ionization measurements of trimethylamine in methane and triethylamine in ethane are presented as a function of perturber number density at various noncritical temperatures and near the perturber critical isotherm. Critical point effects are observed that are similar to those seen in atomic fluids. A two-Yukawa potential is shown to model the perturber/perturber interactions accurately by calculating the phase diagram of the perturber fluids, and using this potential the local Wigner–Seitz model for the energy of the excess electron is successfully applied to these molecular systems.