Raman-, IR- und FIR-Messungen an wasserfreiem Natriumperchlorat NaClO4 im Temperaturbereich zwischen 90 und 600 K

Abstract

Abstract This paper reports a detailed study of the k = 0 vibrational spectra of the anhydrous orthorhombic anhydrite type sodium perchlorate NaClO4 in the temperature range from 90 to 600 K. The i.r., FIR and Raman spectra have been recorded and discussed on the basis of both the unit cell group and the site group of the ClO4− ions. The assignment of the modes was done with help of Raman single crystal measurements. Dynamic interactions of the vibrations of adjacent ClO4− ions are very small (Davydov splitting 40 cm−1). Splitting of the vibrations due to isotopic effects of chlorine atoms has not been observed with exception of one mode of the fundamental ν4 of the perchlorate ions. The site group splittings diminish at temperatures above 480 K and disappear with the exception of a shoulder at the bending fundamental ν2 above 581.3 K, the temperature of the phase transition to the cubic high temperature form (NaCl-type). The librational fundamentals and the translatory modes of NaClO4 are very broad, even at 90 K and of unusually weak intensity in the Raman spectra.