Infrared and Raman spectra have been recorded for room-temperature-phase, powdered samples of LiNO3, NaNO3, KNO3, RbNO3, CsNO3, AgNO3, and TlNO3. For the trigonal systems, the nitrate pairs LiNO3, NaNO3 and RbNO3, CsNO3 give almost identical spectra. For the orthorhombic systems, AgNO3 and TlNO3 give similar spectra, whereas that of KNO3 is significantly different. Site and correlation field perturbations are considerably more pronounced in the antisymmetric stretching region (ν3 ca. 1400 cm−1) than in the antisymmetric bending region (ν4 ca. 700 cm−1). Although lifting of the degeneracy of E′ modes was frequently observed, the reported split of the ν4(E′) mode (ca. 716 cm−1) of the aragonite form of KNO3 could not be confirmed. Multiple internal reflectance techniques have been employed to observe the extremely intense ν3(E′) infrared fundamental ca. 1400 cm−1.
