The authors have measured and calculated the dependence of the Raman phonon intensities of YBa2Cu3O7 on laser frequency. The local-density approximation and the linear muffin-tin-orbital method were used for the calculations. They find good agreement not only in the absolute phonon intensities in zz or xx/yy polarization but also in the shape of the resonance profiles. These results indicate that the local-density approximation gives an essentially correct description of the band structure and of the electron-phonon interaction +or-2 eV around the Fermi energy. They interpret the data in terms of specific interband transitions and estimate the mode mixing.
 

Physical Review Letters, 65 3048-51, 1990.