Magnetic excitation spectra of $NaV_2O_5$
  We present low temperature Raman spectra of $NaV_2O_5$ single crystal. The assignation of the observed modes is done on the basis of Monte Carlo calculation of excited states of Heisenberg dimerized Hamiltonian, without frustration. We found a good agreement between measured and calculated magnetic excitations for $\delta=0.048$ and $J=452 K$. The singlet-triplet, singlet-singlet excitations as well as two-magnon mode are observed to be at 66, 127 and 132 cm^{-1}. 
K. Ladavac(1), M. J. Konstantinovic(1), A. Belic(1), Z. V. Popovic(1),   A. N. Vasil'ev(2), M. Isobe(3) and Y. Ueda(3) ((1) ...