Atmospheric pressure operation of a KrF laser is suitable for large‐aperture laser modules in which several technical limitations on the ICF driver design are overcome by the use of aerodynamic windows instead of the conventional solid optical windows. We experimentally studied atmospheric‐pressure operation of the KrF laser pumped by 50‐ns electron beams. For a 1‐atm mixture of Kr and F2without diluent, a specific output energy of 4.2 J/1 was obtained with an intrinsic efficiency of 5%, which was comparable to that from normal 10% Kr mixture. According to the results of fluorescence measurements, a large amount of Kr2F* is formed via three‐body collisional quenching by high‐concentration Kr even in the atmospheric‐pressure mixture. Code calculations indicate that a higher excitation rate improves the intrinsic efficiency by reducing three‐body quenching especially in Kr‐rich mixtures, and that a specific energy in excess of 10 J/1 is realizable.