Selection rules for Brillouin light scattering from eigenvibrations of a   sphere
  Selection rules governing Brillouin light scattering from the vibrational eigenmodes of a homogeneous, free-surface submicron sphere have been derived using group theory. The derivation is for the condition where the sphere diameter is of the order of the excitation light wavelength. Well-resolved spectral data obtained from Brillouin light scattering from submicron silica spheres provide experimental verification of the selection rules. 
Y. Li, H. S. Lim, S. C. Ng, Z. K. Wang, M. H. Kuok