LOW-FREQUENCY RAMAN-SCATTERING IN NORMAL AND DEUTERATED ICE I-H

Low-frequency Raman spectra of H2O and D2O single crystals at differen t temperatures have been measured by using a DMDP2000 spectrometer. Th anks to the performances of the spectrometer, we have been able to mea sure spectra very close to the elastic line. Present data extend those already measured by Briganti et al. [Solid State Commun. 42, 493 (198 2)] to a lower frequency range and to deuterated samples. We demonstra te the existence of a quasielastic component in both deuterated and no ndeuterated samples which does not show any appreciable isotopic effec t. This allows us to rule out the assignment of the quasielastic compo nent to a relaxing dynamics of the proton-(deuteron) disordered sublat tice. On the contrary, the temperature dependence of the intensity of this component suggests to assign it to the quasielastic contribution of the second-order Raman scattering.