Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Resonant Raman scattering in NaV2O5 as a probe of its electronic
  structure   In order to investigate the origin of the phase transition observed in
NaV$_2$O$_5$, as well as its electronic structure, we have measured Raman
intensities as a function of the laser wavelength above and below the phase
transition temperature. In the polarized Raman spectra at room temperature we
observe resonant enhancement of the 969 $cm^{-1}$ phonon mode when the laser
energy approaches 2.7 eV, presumably related to the (p-d) electron hopping
band, $O_3$($p_y$)-V($d_{xy}$), at 3.2 eV. The 969 $cm^{-1}$ mode originates
from the stretching vibrations along the c-axis involving the V-$O_1$ bonds.
Since an ellipsometric determination of the dielectric function $\epsilon_{cc}$
yields no structure in the 1.7 to 5.5 eV photon energy range, we conclude that
plane bonds couple strongly with the apical oxygens leading to a large Raman
efficiency. In the low-temperature Raman spectra, almost all modes that become
active below the phase transition temperature T$_c$=34 K show resonant
behavior. The most interesting ones, those at 66 and 106 $cm^{-1}$, possibly of
magnetic origin, exhibit a resonant intensity enhancement, approximately by an
order of magnitude, for laser photon energies around 1.85 eV with respect to
2.43 eV. This resonance effect may be associated with a weak absorption band
around 2 eV. Finally, a destructive interference between the resonant and the
nonresonant contribution to the Raman scattering amplitude (i.e. an
antiresonance) is found in the spectra for most of the (bb) low-temperature
modes.

2
The categories of this paper are: math
3
The categories of this paper are: physics
19
The categories of this paper are: eess
23
The categories of this paper are: solv-int
21
The categories of this paper are: adap-org
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
13
The categories of this paper are: quant-ph
14
The categories of this paper are: math-ph
27
The categories of this paper are: comp-gas
34
The categories of this paper are: chem-ph
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
24
The categories of this paper are: dg-ga
5
The categories of this paper are: gr-qc