Far-Infrared Properties of Cuprous Oxide

The transmission and reflectance of cuprous oxide has been measured from 6 to 250 \ensuremath{\mu} and analyzed by classical dispersion theory. The two infrared-active vibrational frequencies are given by ${\ensuremath{\nu}}_{1}=613$ ${\mathrm{cm}}^{\ensuremath{-}1}$ and ${\ensuremath{\nu}}_{2}=146.0$ ${\mathrm{cm}}^{\ensuremath{-}1}$ with corresponding longitudinal-mode frequencies of 638 and 149 ${\mathrm{cm}}^{\ensuremath{-}1}$. The maximum values of the extinction coefficient are calculated to be 2.7 and 4.0, respectively, for the two modes; both are higher than the literature values. The high-frequency and static dielectric constants are found to be ${\ensuremath{\epsilon}}_{\ensuremath{\infty}}=6.6$ and ${\ensuremath{\epsilon}}_{0}=7.6$, respectively.