  Ultraviolet (UV) scattering on quantum crossbars (QCB) is an effective tool
for probing QCB spectral properties, leading to excitation of QCB plasmon(s).
Experimentally, such a process corresponds to sharp peaks in the frequency
dependence of the differential scattering cross section. The peak frequency
strongly depends on the direction of the scattered light. As a result, $1D\to
2D$ crossover can be observed in the scattering spectrum. It manifests itself
as a splitting of single lines into multiplets (mostly doublets). The splitting
magnitude increases with interaction in QCB crosses, while the peak amplitudes
decrease with electron-electron interaction within a QCB constituent.
