  We investigated temperature dependent optical conductivity spectra of
Nd0.7Sr0.3MnO3 single crystal. We found that polishing and surface scattering
effects on the Nd0.7Sr0.3MnO3 crystal surfaces could significantly distort the
optical responses, especially in the mid-infrared region. However, oxygen
annealing and gold normalization processes seemed to remedy the distortions. We
found that the spectral weight of Nd0.7Sr0.3MnO3 in the metallic state might be
composed of a Drude carrier term and a strong incoherent mid-infrared
absorptions. The temperature dependence of the spectral weight suggests that
the electron-lattice coupling should be important in optical properties of
colossal magnetoresistance manganites.
