  We have measured the optical conductivity of single crystal LuMnO3 from 10 to
45000 cm-1 at temperatures between 4 and 300 K. A symmetry allowed on-site Mn
$d$-$d$ transition near 1.7 eV is observed to blue shift (~0.1 eV) in the
antiferromagnetic state due to Mn-Mn superexchange interactions. Similar
anomalies are observed in the temperature dependence of the TO phonon
frequencies which arise from spin-phonon interaction. We find that the known
anomaly in temperature dependence of the quasi-static dielectric constant
epsilon_0 below the T_N ~90 K is overwhelmingly dominated by the phonon
contributions.
