Spin-Flip Raman Scattering in Cadmium Sulfide

Extremely powerful Raman scattering is seen from CdS using the 4880 {} laser line in the presence of a magnetic field. This scattering occurs from the magnetically split ground states of donors and acceptors, that is, from bound electrons and holes. The effect depends upon the geometry of the experiment, with a maximum differential cross section of about 4×{}10^-18 cm²/sr being observed. A theory is developed which gives a quantitative understanding of the phenomenon as taking place via bound exciton states. Because the failure to conserve energy in the intermediate state is small compared with the valence-band spin-orbit splitting, the spin-orbit coupling for the valence band is effectively infinite. This valence-band spin-orbit coupling is responsible for the electron (donor) spin-flip scattering. The oscillator strengths of transitions giving the bound excitons have been measured and found to be very large (near 10 for donors).