Second-harmonic generation and stimulated Raman effects for a plasma are calculated by the same methods that have been used for bound electrons. The nonlinear susceptibility describing the stimulated Raman effect in a gaseous or metallic plasma is 6 to 10 orders of magnitude smaller than the corresponding effect in liquids. This process in a plasma can also be described as the parametric interaction between a damped plasma wave and two light waves. The second-harmonic generation from a plasma boundary is dominated by a surface term which originates from the discontinuity in the normal component of the electric field. It is shown that the observed second-harmonic generation from metallic silver probably stems from bound ion cores in the surface layer rather than from a plasma surface term.

• Received 6 August 1965

DOI:https://doi.org/10.1103/PhysRev.141.298