Vibrational spectroscopic analysis of lithium hydrazinium sulfate

Abstract

The low temperature polarized Raman spectra of lithium hydrazinium sulfate, LiN 2H 5SO 4, have been measured in the range 5–3500 cm −1. The symmetry-based assignments for the observed modes are given. The room temperature polarized i.r. reflectivity spectra in the range 200–4000 cm −1 were also measured to verify the presence of extensive TO—LO splitting in the sulfate ion ν 3 and ν 4 internal optic modes. In the lattice mode region, the lithium ion external optic modes are identified, and the spectra of the deuterated analog allow the identification of several modes due primarily to the external motions of either the sulfate or hydrazinium ions. Other lattice modes are found to be a mixture of sulfate and hydrazinium ion external motions. Coupling of the sulfate ion ν 3 modes and the hydrazinium ion group bending modes prevents an unambiguous assignment of the bands in the 1050–1200 cm −1 spectral region. The N—H stretching region spectra contain a larger number of modes than predicted by a factor group analysis. These extra modes are discussed in terms of resonance interactions of the N—H stretching fundamental modes with overtones and combination modes.