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Room-temperatureRaman spectra of high-quality single-domain BaTi03 crystals are reported. The frequencies of the Raman-active long-wavelength optical phonons are determined and shown to be in reasonable agreement with the Lyddane-Sachs-Teller (LST) relation as well as infrared reQectivity data. The eGects of mode damping on the Raman line shape are discussed using a classical lattice-polarization-Quctuation model for the Raman scattering process. Based on this model, it is shown that the soft E mode is overdamped, and at 25'C has an undamped mode frequency A&TO of 36&3 cm~and a damping constant F of 1.1&0.1.The temperature dependence of co~o is given and found to be consistent with the LST relation, The soft A& mode is not observed, but is estimated from the LST relation and infrared reQectivity data to be heavily damped (F=0.5) and to have an undamped mode frequency of 180+10 cm '.

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