Ultraviolet Optical Properties of Diamond

The absolute reflection spectrum of type IIa diamond was measured at room temperature from 4 to 30 eV and analyzed by dispersion techniques to obtain the optical parameters. Structure observed in the dielectric constant near 7, 12, 16, 20, and 24 eV was attributed to interband transitions at critical points in the joint density-of-states function. The new high-energy structure near 16, 20, and 24 eV was assigned to transitions near the $L$ point of the Brillouin zone. Experimental interband transition energies are compared to band theory calculations.