Transient refractive index was calculated for an e-beam pumped XeF laser having initial concentrations Ne:Xe:NF3::95.5:4.3:0.2. The calculation used Ne in excited states including the transition array 3s yields 4p and all other constituents in ground state. Lines in 3s yields 4p array may be resonant with XeF radiation. To obtain the transient populations for Ne, a modification was made to a Naval Research Laboratory computer code which typically accounts for 180-200 reactions involving 50-60 different species. The modified program included populations in 12 electronic configurations of Ne. Electron beam current was changed 10% at constant voltage to simulate the influence of a hibachi shadow. For a nonresonant laser wavelength, an optical pathlength in the laser, L, less than 35 meters will have distortion delta/lambda less than 0.1; however, for a laser wavelength in resonance with Neon, L of only 0.11 meter will cause delta/lambda = 0.1. The difference in optical pathlength is delta.