Abstract: The inventive method for carrying out chemical reactions consists in supplying reaction gas from the source (2) thereof to a vacuum reaction chamber (4), forming a supersonic reaction gas stream (1) in said reaction chamber and in activating said reaction gas stream by exposing it to the action of an electron beam (6) in such a way that an electron-beam plasma (8) is produced. The supersonic reaction gas stream is formed in such a way that a decompression zone (5) is produced in the center thereof at entry into the vacuum reaction chamber. Said decompression zone has a density which is lower with respect to the density of the zones adjacent thereto. The action of the electron beam on the reaction gas stream is carried out by introducing said electron beam into said decompression zone.