Infrared and Raman Spectroscopic Studies of Solid Alkali Metal Nitrites

Abstract

Infrared and Raman spectra of solid LiNO,.H,O, LiNO,, NaNO,, KNO,, and CsNO, are presented and discussed. Pronounced changes in the spectra of LiNO,.H,O during dehydration to anhydrous LiN0, are interpreted as evidence for an ordered distribution of NO2-ions over two non-equivalent sites (akin to linkage isomerism) in anhydrous LiN0,. The frequencies of the internal modes of the nitrite ion shift to lower values with increasing cation size. Vibrational bands due to nitrate ion present as an impurity are assigned.Les spectres infrarouge et Raman des LiNO,.H,O, LiNO,, NaNO,, KNO, et CsNO, sont presentks et discutks. Les changements prononcks qui se produisent dans les spectres pendant la dkshydratatlon du sel LiN02.HZ0 B LiNOz sont interprktks comme preuve d'une distribution ordonnde des ions NOzsur deux sites non tquivalents (vkritable isomkrisme de liaison) dans le sel anhydre LiN0,. Les frkquences des modes internes de l'ion nitrite sont abaisskes lorsque la dimension du cation augmente. Les bandes vibrationnelles dues a l'ion nitrate present comrne impuretk sont assignkes.Canadian Journal of Chemistry, 49, 1289 (1971) Introductionreported to decompose at 200 "C before melting An interest in the vibrational spectra of con-at 225 "C (19). The solid potassium and caesium centrated electrolyte solutions and in N+ nitrites take the form of unmanageable plastics vibrations of ions similar to nitrate (1) has recently with of water; however, caused us to focus attention on metal nitrites, definite hydrates of these are many of which are extremely water soluble. (19,20). Sodium nitrite, on the other hand, forms When interpreting data for concentrated solu-well defined single crystals. The discovery by tions and melts, knowledge about the probe ion Strijk and MacGillavr~ (21) of the ferroelectric in static, cationic environments is an asset. Al-phase transition in NaNO, prompted considerthough NaNO, has been extensively studied and able infrared (12-15) and Raman (l 6, 7, KNO, to a lesser extent (2-17), no systematic studies, most of which have been performed on comparison including other alkali metal nitrites single and concerned with various has been reported. this study Raman spectra phenomena associated with order-disorder ferroand multiple internal reflectance (m.i.r.) infrared spectra of powders have been obtained. The An consideration prior the m.i.r. technique is particularly useful for dis-measurement of the physical properties of nitrites closing features of intense absorption bands, the be sample purity. The assay positions of which are not distorted by con-reagent grade KN02 varies 89 97% tfibutions from longitudinal optical modes "itrite ; even NaNO2 seldom exceeds 98% minior Christiansen filter effects (18). An interesting mum nitrite assay.are H20, consequence of this study has been the observa-OH-, C1-, C032-, and NO3-; of these the tion of spectral changes on dehydration of the NO3-is most serious. Potassium nitrite is known lithium nitrite monohydrate which can be to form a solid solution with NO3-...

High-pressure vibrational spectroscopy of sulfur dioxide

“…10 Furthermore, their interpretation of phase III is also inconsistent with later extensive Raman investigation. 24 Therefore, although we have observed similar high-pressure behavior of SO 2 , we favor the interpretation indicated by factor group analysis, where the unit cell contains monomeric SO 2 molecules and the splittings are the result of interactions between neighboring molecules in an acentric cell. The additional lattice modes observed in the present study ͑Table I͒, in excellent agreement with Swanson et al, 13 indicate that there are more than two molecules per primitive cell.…”

“…6,7 For acentric crystals the TO/LO splittings may be observed in the Raman spectra if the mode is simultaneously IR active. [21][22][23][24] At both room and low temperatures, we observed two components of the v 1 mode corresponding to the TO and LO vibrations with A 1 symmetry at most pressures ͑Figs. 1 and 3͒.…”

Luminescent determination of nitrite traces in water solutions using cellulose as sorbent

“…First, there can be the centers formed by MA NO − 2 located in the volume of the MNO 2 particles. These centers have to reveal spectral features similar to the cases of metal alkali nitrite salts and alkali-halide crystals doped with MA NO − 2 (Sidman, 1957;Brooker and Irish, 1971;Kushnirenko et al, 1984;Belii et al, 1984Belii et al, , 1988Kononenko et al, 1985). Such type centers dominate PL emission of the area shown in Fig.…”

Polymer-Oxide Composites: Toward New Optical Materials

“…5, curve 4) differ radically. In fact, the NaNO 2 oxide can itself contribute to the luminescence of composite, while the CsNO 3 oxide did not show luminescence at any conditions [57][58][59][60]. It means that excitation spectrum 3 in Fig.…”