[en] A soft-x-ray laser utilizing electron pickup by a stripped nucleus is proposed. A particular example using electron exchange between hydrogen and an α particle is analyzed and is shown to produce inversion between the He₂⁺/sub p/ and He⁺/sub ls/ levels giving stimulated emission at 304 A. In this scheme the α particles are swept along the target at the speed of light. The cross sections involved in the electron pickup in a hydrogen target and subsequent collisional deexcitation are analyzed to ascertain the optimum target thickness for population inversion. Also the effects of atomic collisions on the stimulated-emission cross section are estimated (Doppler broadening). The dynamics of the beam including focusing and space-charge effects are discussed. The stimulated-emission cross sections for a gas and a solid thin-film target are calculated. For a 30-mA α-particle current and a 10-cm lasing length, gains of 1.1 and 50 are estimated. (U.S.)