Raman scattering investigation of Cu¹⁸O

Raman scattering experiments have been carried out on powdered samples of cupric oxide (CuO) grown with the 18 O isotope. The phonon frequencies have been measured and compared to those of Cu 16 O. The isotopic frequency shifts of the phonon modes have also been compared with the predictions of a lattice dynamics model. Previous low temperature experiments on Cu 16 O revealed a mode at 240 cm -1 that was attributed to a magnetic excitation. The present results are consistent with this interpretation in that the same mode is observed to be unshifted in the spectra from Cu 18 O at low temperatures. A broad peak is also observed in the low temperature spectra at higher energies. This feature has a maximum at about 2100 cm -1 , is believed to arise from electronic scattering and is perhaps, at least in part, due to two-magnon scattering.