Raman spectra of anatase have been observed in natural and synthetic crystals. Both crystals show the same spectral features. The Raman band occumng at 516 cm-' at room temperature is split into two peaks centred at 519 cm-' and 513 cm-' at low temperature (73 K). The six Raman active fundamentals predicted by group theory are all observed and assigned. The spectra are analyzed by a simple model considering only short-range forces and the calculated vibrational frequencies are in good agreement with the observed Raman frequencies.

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Coherent effects in synchrotron radiation (SR) have been observed for the first time from 180-MeV short electron bunches of 2.5 mm using the Tohoku 300-MeV Linac. The intensity of the coherent SR was about 10 5 times as strong as that of incoherent SR in the wavelengths of 0.4-2.2 mm. This enhancement factor corresponds to the number of electrons in a bunch. The SR intensity showed a quadratic dependence on the electron beam current. The radiation was mainly polarized in the orbital plane. The possibility of induced rf in a vacuum chamber was excluded experimentally.

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