Infrared study of spin-Peierls compound alpha '-NaV2O5

Infrared reflectance of alpha-NaV2O5 single crystals in the frequency range from 50 to 10 000 cm(-1) was studied for a, b and c-polarisations. In addi tion to phonon modes identification, for the a-polarised spectrum a broad c ontinuum absorption in the range of 1D magnetic excitation energies was fou nd. The strong near-IR absorption band at 0.8 eV shows a strong anisotropy with vanishing intensity in c-polarisation. Activation of new phonons due t o lattice dimerisation were detected below 35 K as well as pretransitional structural fluctuations up to 65 K. (C) 1999 Elsevier Science B.V. All righ ts reserved.