Vibration Frequencies of NO2− and NO3− Ions in KBr Crystals

Abstract

Infrared-absorption spectra of doped KBr crystals at temperatures of approximately 8°K were measured in the wavelength range 2 to 15 μ. From the absorption spectra of crystals doped with NO2− and NO3− ions, and with ions enriched in the isotopes 15N and 18O, frequencies of normal vibrations of six isotopic NO2− molecules, and eight isotopic NO2− molecules were determined. These frequency values were used to calculate a set of force constants for NO2− and NO3− ions in the KBr lattice, using the most general harmonic force field (GFF). In mdyn/Å units, values obtained for NO2− were: fr=7.50, frr=1.66, frα=0.39, fα=1.67, and for NO3−: fr=7.62, frr=1.43, (fα—fαα)=1.09, (frα—frα′)=−0 .48, fγ=1.506. In crystals doped with divalent metal ions as well as NO2− and NO3− ions, new absorption bands appeared. These were perturbations of the vibrational frequencies of NO2− and NO3− ions, caused by association between divalent metal ions and NO2− and NO3− ions. In the case of NO3−, the doubly degenerate asymmetric stretching band was split into two nondegenerate bands by the perturbation, which is thus almost certainly caused by a nearest-neighbor association between metal and nitrate ions. While the other frequency shifts of nondegenerate vibrations can give no information about the symmetry of the surrounding lattice, they can also be explained by a nearest-neighbor interaction between divalent metal and NO2− and NO3 ions.

Conflicting Observations Resolved by a Far IR and UV/Vis Study of the NO3 Radical

“…Due to a pseudo-JahnTeller coupling to the excited B $ 2 E' state, the two e'-type modes of NO 3 shift considerably to lower wavenumbers compared to those of the nitrate anion (1383 and 715 cm À1 [30] ). This coupling probably also gives rise to the unexpectedly low infrared intensity of the n 3 fundamental.…”

Infrared and Raman Spectroscopic Studies of Solid Alkali Metal Nitrites

“…This band may be due to either isotopicspecies 15~1602-or 14N160180-; expected intensity ratios based on natural isotopic abundances are 0.00366 and 0.00413, respectively. Sato et al (12) assigned a band at -(v, -20) cm-' in the NaNO, spectrum to the 15N160,-species; however, 15N isotopic substitution studies (2,4,9) have firmly established that the v, mode of NO,-shifts only 5 cm-' on 15N substitution. Kato and Rolfe (9) have assigned a band at (v, -21) cm-I to the 14N1601*0-species.…”

Influence of Pt–Ba Proximity on NO x Storage–Reduction Mechanisms: A Space- and Time-Resolved In Situ Infrared Spectroscopic Study

“…The other bands are assigned to nitrates; the combination mode of m 1 ? m 4 of ionic type nitrate at 1,770 cm -1 [23,26], adsorbed bidentate nitrate species [10,27,28] at around 1,585 cm -1 , and symmetric stretching mode of nitrate [27] at 1,028 cm -1 , which is normally infrared inactive unless its structure is distorted. This band is, therefore, assigned to surface nitrates.…”

“…1C). The intense band at 1,204 cm -1 is assigned to the m 3 vibration of nitrites [20][21][22][23][24][25]. The other bands are assigned to nitrates; the combination mode of m 1 ?…”