Field enhanced photoemission is used to measure the density dependent quasi-free electron energy V-0(rho) in the strongly absorbing gas N-2 for the first time. V-0(rho) in N-2 was obtained from low density to the density of the triple point liquid, at noncritical temperatures and on an isotherm near the critical isotherm. A novel critical point effect is observed and is accurately explained by the local Wigner-Seitz model. (C) 2012 Elsevier B.V. All rights reserved.