Vibrational Spectra of Ammonium and Other Scheelitehyphen;Type Perrhenates

摘要

The farhyphen;infrared and laserhyphen;excited Raman spectra of several scheelitehyphen;type perrhenates have been recorded at 77deg;K and room temperature in order to obtain frequencies and symmetry assignments for the lattice modes. Both NH4ReO4and ND4ReO4were studied to separate ammoniumhyphen;ion translations and librations. At 77deg;K the ammoniumhyphen;ion librational mode is observed at 264 cmminus;1in NH4ReO4and 194 cmminus;1in ND4ReO4. Upon warming to 300deg;K, the ammoniumhyphen;ion librational mode disappears and is unobservable in both the farhyphen;ir and Raman spectra. The Ramanhyphen;active ammoniumhyphen;ion fundamental modes have also been observed in both NH4ReO4and ND4ReO4. The temperaturehyphen;dependent changes in the intensities and linewidths of the ammoniumhyphen;ion fundamentals and lattice modes indicate that the ammoniumhyphen;ion motion undergoes a change between 77 and 300deg;K.