The diffusivity of tritium in rutile single crystals has been measured parallel to the a and c axes in the temperature range 250–900 °C. Raman-scattering measurements were also made to aid in identifying a nonpolar tritium species involved in the diffusion process. Two species, OT− ions and T2 molecules, are involved in tritium migration. The OT− ions dissociate preceding each tritium jump. Along the a axis the T2 molecules diffuse four orders of magnitude slower than the T+ ions associated with OT−. No dependency of the tritium diffusivity upon the rutile defect structure was observed.
Infrared spectra of Ti02 single crystals containing either hydrogen, deuterium, or tritium were measured at 300, 77, and 8 K. Bands observed at 3276, 2437, and 2065 cm ' near 300 K are, respectively, assigned to OH, OD, and OT based on a two-term anharmonic-oscillator model of the hydrogenic species. The frequencies were also analyzed by using a linear hydrogen-bonded model with harmonic forces, but the correlation between frequencies and bandwidths was at variance with that of known H-bonded systems. The absorption strength per ion of OT was calculated at several levels of approximation, and the best value determined was aT --9.24 X 10 ' cm. The harmonic and anharmonic mean-square displacements of OH, OD, and OT were calculated, and the differences bet;ween these quantities reflect the changes in the infrared bandwidths with reduced mass.
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