Resonant Raman Scattering under Two-Photon Excitation of Excitonic Molecules in CdS

Abstract

Two-photon-resonant Raman scattering under the giant two-photon excitation of excitonic molecule has been observed from various scattering directions, and two types of Raman scattering, M T and M M are found. The transverse and mixed modes of the \(A(\varGamma_{5})\) exciton state are left behind in the M T and M M Raman processes, respectively. These Raman scatterings reflect the characteristic dispersions of their respective exciton states, and conform to the geometrical selection rules derived on the assumption that the excitonic molecule state has the \(\varGamma_{1}\)-symmetry. A non-linear absorption peak due to the giant two-photon absorption is found at 2.5506 eV (λ=486.10 nm) with the use of intense probe light. The binding energy of excitonic molecule is found to be 4.4 meV for two \(A(\varGamma_{6})\) triplet excitons.