Raman Spectra and Lattice Dynamics of Tellurium

The Raman spectrum of trigonal tellurium has been obtained at 295 and 90 °K. The Raman-active $A_1$ singlet and two $E$ doublets are identified by the scattering polarization selection rules, and the $E$-mode LO-TO splittings and linear wave-vector shifts are observed. The natural linewidths of the phonons are resolved and some weak second-order structure is evident. A spectrum of amorphous tellurium is also presented. The data on trigonal tellurium, together with neutron-scattering and infrared reflectivity measurements, are used to construct a lattice-dynamical model based on a symmetrized Fourier-expansion scheme incorporating generalized noncentral forces.