Abstract: Method and apparatus for generating a nearly mono-energetic beam of atoms at velocities on the order of several km/sec (energies of 1-10 eV) and for achieving modification of the surface properties of a target by the beam, including surface erosion, reaction with the beam species, cleaning and coating, all over a large area. A gas or gas mixture is forced through a nozzle throat into a previously evacuated expansion nozzle resulting in the acceleration of the gas in a confined flow. Laser radiation is applied to the gas flow to cause breakdown and dissociation of the gas into an atomic plasma. The plasma is allowed to expand within the nozzle cone reaching a high velocity in the desired range. The beam is generated within a vacuum chamber to maintain the purity of the gas components and prevent collisional effects. The beam is used to modify the properties of a target material placed in the path of its flow and its atoms may react with surface components to form a molecular coating.