Second-harmonic generation in centro-symmetric media

The magnetic-dipole and elec.-quadrupole contributions to second-harmonic generation (SHG) of centro-sym. media were studied. The phenomenol. parameters a, b, g can be arranged to form an effective .hivin.cs(2)-tensor, which describes dipole-forbidden SHG as the effect of a surface layer upon excitation with a single plane electromagnetic wave. An exptl. technique is proposed allowing a detn. of the usually very small g term due to magnetic-dipole interaction using coherent compensation of its contribution by a coverage with an appropriate dye monolayer