Infrared Spectral Emittance and Optical Properties of Yttrium Vanadate

The infrared spectral emittance $E$ of single scrystals of YV${\mathrm{O}}_4$ has been examined near 4.2 and 77°K in the wavelength range 4-125 μm. Of the expected seven active transverse optical modes at k∼0, six have been observed and assigned to their symmetry species based on their polarization with respect to the crystalline axes. The observed frequencies of the transverse optic $E_u$ modes were 196, 261, and 788 ${\mathrm{cm}}^{-1\mathrm{}}$; and for $A_{2u}$ modes, 310, 455, and 803 ${\mathrm{cm}}^{-1\mathrm{}}$. The relation between emittance and reflectance, $E=1-R$ in the opaque region of lattice vibrations, permits one to determine the reflectance $R$. By least-square-fitting the reflectance data to an independent set of damped harmonic oscillators, infrared dispersion parameters were determined for the $E_u$ vibrations.