  We study the thermostatistical fluctuations of a single Delrin monomer on a
granular lattice of dimer particles using both experiment and simulation. The
goal is to examine the collision frequency, energy injection, and sidewall
effects on a single second-layer particle in a bi-layer granular gas
experiment. Non-Gaussian velocity statistics are observed for the single
particle of the top layer and result from the presence of defects in the first
layer. These deviations are not directly due to the presence of the boundary
wall, since the form of velocity distributions is quite spatially homogeneous,
but are the consequence of the presence of a few mobile defects in the first
layer.
