  We report plane-polarized Raman scattering spectra of iron oxypnictide
superconductor NdFeAsO$_{1-x}$F$_x$ single crystals with varying fluorine $x$
content. The spectra exhibit sharp and symmetrical phonon lines with a weak
dependence on fluorine doping $x$. The temperature dependence does not show any
phonon anomaly at the superconducting transition. The Fe related phonon
intensity shows a strong resonant enhancement below 2 eV. We associate the
resonant enhancement to the presence of an interband transition around 2 eV
observed in optical conductivity. Our results point to a rather weak coupling
between Raman-active phonons and electronic excitations in iron oxypnictides
superconductors.
