RAMAN SPECTRA INVESTIGATION OF TEMPERATURE PHASE TRANSITIONS IN ALKALI METAL PERCHLORATES. V.I. Snejkov, North Caucasus Scientific Center, 140, Pushkinskaya, Rostov-on-Don, 344006, Russia

It was discribed the obtained Raman spectra for wide temperature region (at room temperature to metling one). The degeneration of internal moleculer frequences is increased with growth of temperature and differ from as room - temperature data so ones predicted by symmetrical analysis. For example the Y2 mode of LiClO₄ contains two line for both solid phases. This fact indicates the higher temperature phase has a noncubic distorsion. For (K, Rb, Cs)ClO₄ the Y1 mode consist of only one line. The other mode (Y3) contains two lines for low teperature state which go out after phase transition. Such behaviour does not coincide with generally admitted interpretation of nature of these frequences. On the base of the obtained data it was proposed the new interpretation main modes (Y1, Y2, Y3) and elobarated the teoretical model explaining in frame work of slow symmetry the temperature behaviour of Raman spectra. This model connects the significances of frequance splittiny with the temperature stracture distorsin. In particuler the higher phase is pseudocubic (the tetragonal type) for NaClO₄ and it is cubic for (K, Rb, Cs)ClO₄. The last have tetragonal low temperature phase turning into ortorombic one under the room temperature.