Energy extraction measurements are obtained with a 350 ns electron-beam pumped KrF laser (Ar diluent) at Kr concentrations from 4-99.6 percent. During the measurements, the F2number density is held constant at cm-3, and the average pump rate is maintained at ≈120 kW/cm3by adjusting the total pressure of the gas mixtures in order to compensate for the different electron stopping powers of Ar and Kr. For the 4, 10, and 99.6 percent Kr cases, total pressures are 1040, 1004, and 665 torr, respectively. Average output efficiencies in percent of 9.3 at 4 percent Kr, 11.2 at 10 percent Kr, and 9.2 at 99.6 percent Kr are obtained. Peak power efficiencies in percent of 9.6 at 4 percent Kr, 12.5 at 10 percent Kr, and 11.6 at 99.6 percent Kr are derived from the data. Our computer model predictions agree with the results.