  Infrared reflectance measurements were made on the single crystal pyrochlore
Cd$_{2}$Os$_{2}$O$_{7}$ in order to examine the transformations of the
electronic structure and crystal lattice across the boundary of the metal
insulator transition at $T_{MIT}=226K$. All predicted IR active phonons are
observed in the conductivity over all temperatures and the oscillator strength
is found to be temperature independent. These results indicate that charge
ordering plays only a minor role in the MIT and that the transition is strictly
electronic in nature. The conductivity shows the clear opening of a gap with
$2\Delta=5.2k_{B}T_{MIT}$. The gap opens continuously, with a temperature
dependence similar to that of BCS superconductors, and the gap edge having a
distinct $\sigma(\omega)\thicksim\omega^{1/2}$ dependence. All of these
observables support the suggestion of a Slater transition in Cd$_{2}%
$Os$_{2}$O$_{7}$.

Strongly Correlated Electrons