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Rhumb.-Les phonons optiques (k-0) de CuInS2, AgInS2 et CuFeS, ont ete analyses par des mesures d'absorption et de reflexion dans la region de 1 000 jusqu'a 50 cm-1. La determination des frequences des phonons optiques transversaux et longitudinaux a et6 effectuk B I'aide dqCquations Kramers-Kronig ainsi que de modtles classiques d'oscillateurs. Les rksultats sont cornparks aux spectres connus de CuAIS,, CuGaS2 et AgGaS2. Une comparaison systematique des frequences des modes montre quc les constantcs de force des differents coniposes 1-111-S2 sont presque egales. Les differences des frequences des modes correspondants paraissent dependre principalement des differentes masses des cations.

We have measured and analysed the Raman-scattering and far-infrared spectra from unoriented n-and p-type Hg, -,Cd,Te with x 0.21. Measurements were made in the 80-180 cm" frequency region at temperatures of 10 and 80 K. Comparison of the n-and p-type spectra leads to the conclusion that the electronic contribution to the Raman spectra is small. In particular, the data show that the 135cm" feature originates in lattice effects and may be related to the Te-3Hg-Cd combination as previously suggested. The weak but distinct fine structure present in the CdTe-like reststrahlen band at -153 cm" is tentatively assigned to be a result of localised oscillations of Cd ions in the alloy lattice. A study of the spectral changes between 10 and 80 K clearly indicates a softening of the HgTe-like TO phonon

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