Charge and sodium ordering in beta-Na_0.33V_2O_5
  Polarized Raman and optical spectra for the quasi one-dimensional metallic vanadate beta-Na0.33V2O3 are reported for various temperatures. The spectra are discussed in the light of the sodium and charge ordering transitions occurring in this material, and demonstrate the presence of strong electron phonon coupling. 
P.H.M. van Loosdrecht, C.N. Presura, M. Popinciuc, D. van der Marel,   G. Maris, T.T.M. Palstra, P.J.M. van Bentum, H. Yamad...