Polarization dependence of the two quantum absorption spectrum of intrinsic excitons in ZnO

The intrinsic exciton spectrum of ZnO at 4.2°K has been investigated by two quantum absorption of light polarized parallel and perpendicular to hexagonal c-axis (light direction normal to c-axis). Three lines are observed with intensity and spectral position depending on polarization of the two interacting beams in respect to the c-axis. They are interpreted as n=2 states of the exciton series A, B and C with 2P₀ and 2P₊₁ envelope.