  We study the interaction of surface acoustic waves (SAWs) with the
contact-based, axial vibrational resonance of 1 \mu m silica microspheres
forming a two-dimensional granular crystal adhered to a substrate. The
laser-induced transient grating technique is used to excite SAWs and measure
their dispersion. The measured dispersion curves exhibit "avoided crossing"
behavior due to the hybridization of the SAWs with the microsphere resonance.
We compare the measured dispersion curves with those predicted by our
analytical model, and find excellent agreement. The approach presented can be
used to study the contact mechanics and adhesion of micro- and nanoparticles as
well as the dynamics of microscale granular crystals.
