LUMINESCENCE AND HYPER RAMAN-SCATTERING DUE TO EXCITONIC MOLECULES IN ZNP2

We have measured luminescence and Raman scattering of a ZnP2 monoclinic crystal in high density excitation of a picosecond pulsed dye laser light at 2 K. An asymmetric luminescence band is observed at 1.549 eV and is found to be associated with the annihilationof a thermalized GAMMA+1 excitonic molecule leaving a GAMMA-2- mixed mode exciton. A resonant hyper Raman scattering has been observed under excitation by a giant two photon absorption in the backward scattering geometry. The observation of this hyper Raman line shows an existence of the excitonic molecule. The binding energy is estimated to be 5.0 +/- 0.4 meV for the GAMMA-1- triplet exciton and 10.4 +/- 0.4 meV for the GAMMA-2- singlet exciton.