The small‐signal gain and absorption of an electron‐beam‐excited KrF* laser mix was measured by probing the excited medium with a frequency‐doubled flashlamp‐pumped dye laser. The mixture contained 0.3% F2, 6% Kr, and 93.7% Ar. The doubled dye laser was used to determine the single‐pass gain or loss of this e‐beam‐excited mixture over the KrF* (2&Sgr;1/2→2&Sgr;1/2) emission band. The KrF* and other relevant excited‐state number densities under the condition of the experiment were determined from a comprehensive kinetic model. The effective KrF* stimulated‐emission cross section was determined by dividing the measured gain per centimeter on line center by the excited‐state number density.