  The vibrations of a coupled pair of isotropic silver spheres are investigated
and compared with the vibrations of the single isolated spheres. Situations of
both strong coupling and also weak coupling are investigated using continuum
elasticity and perturbation theory. The numerical calculation of the eigenmodes
of such dimers is augmented with a symmetry analysis. This checks the
convergence and applicability of the numerical method and shows how the
eigenmodes of the dimer are constructed from those of the isolated spheres. The
frequencies of the lowest frequency vibrations of such dimers are shown to be
very sensitive to the strength of the coupling between the spheres. Some of
these modes can be detected by inelastic light scattering and time-resolved
optical measurements which provides a convenient way to study the nature of the
mechanical coupling in dimers of micro and nanoparticles.
