Results of a hydrodynamic computer code are presented, which describes the expansion of a laser generated plasma into an ambient gas. The theoretical model includes diffusion, thermal conduction, elastic collision interaction and the detailed kinetics of excited atomic and ionic levels. The retarded plasma motion results in a slow electron density decay. Effective electron cooling is achieved in the diffusion region where the plasma mixes with the background gas. Quasisteady‐state population inversions occur in the resulting cold and dense plasma.