Infrared absorption in bulk amorphous As

We report the room-temperature infrared absorption spectrum of bulk $a-\mathrm{As}$. The spectrum shows strong features in two well-separated spectral regions, near 230 ${\mathrm{cm}}^{-1\mathrm{}}$ and between 150 and 110 ${\mathrm{cm}}^{-1\mathrm{}}$ The absorption in $a-\mathrm{As}$ is compared with absorption reported previously for $a-\mathrm{Se}$ and $a-\mathrm{Ge}$. The absorption in all three elemental amorphous materials corresponds to structure in the vibrational density of states and is discussed in terms of a structural model that is based on the atomic coordination and resultant short-range order.