Energy of the quasi-free electron in xenon

Field ionization of trimethylamine and of N,N-dimethylaniline doped into xenon is presented as a function of xenon number density up to the density of the triple point liquid, both at noncritical temperatures and along the critical isotherm. These data exhibit a decrease in the xenon induced shift of the dopant ionization energy near the xenon critical point. The energy of the quasi-free electron, arising from dopant field ionization, in xenon is calculated within a local Wigner-Seitz model to within ±0.3% of experiment at noncritical temperatures and for the critical isotherm.