Raman scattering and exciton luminescence and absorption have been studied in high-purity single-crystal ${\mathrm{Cu}}_2$O at liquid-helium temperature using 4880-Å laser excitation. The Raman-active mode has been unambiguously identified at 515 ${\mathrm{cm}}^{-1\mathrm{}}$, and the first observation made of luminescence from the $n=2, 3, 4$ yellow excitons and their continuum. Comparison of the Raman spectra with the absorption and luminescence spectra near the $n=1\mathrm{}$ exciton has clarified the origin of the strong 220-${\mathrm{cm}}^{-1\mathrm{}}$ Raman feature and yielded evidence for wave-vector-independent and wave-vector-dependent exciton-phonon coupling, respectively, for the ${\Gamma }_{12}^{-}$ and ${\Gamma }_{15}^{-}$ optic phonons.

• Received 29 June 1972

DOI:https://doi.org/10.1103/PhysRevB.6.4753