The polarized transmission infrared spectra between 400 and4000thinsp;cmminus;1and theHesngbnd;Nelaser excited Raman spectra between 30 and 1500 cmminus;1of an oriented single crystal of agr;hyphen;lead azide (PbN6), have been measured and the longhyphen;wavelength vibrational modes have been assigned by factorhyphen;group analysis. The observed splittings are in essential agreement with the reported space groupD2h16minus;Pnma. The Ramanhyphen;active lattice modes are observed in the frequency range30ndash;210thinsp;cmminus;1. The appearance of peaks in the1330ndash;1360minus;cmminus;1region due to the symmetric stretching vibration of the azide ion, in both the infrared and Raman spectra, confirms the presence of fairly asymmetric azide ions in the lattice. A probable relationship between a component of the bending mode frequency of the azide ion and the thermal instability of agr;hyphen;lead azide and related metal azides is pointed out.
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