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The properties of nitrosonium nitrate (NO+NO3−) were investigated following synthesis by laser heating of N2O and N2O4 under high pressures in a diamond anvil cell. Synchrotron infrared absorption spectra of NO+NO3− were measured at pressures up to 32 GPa at room temperature. Raman spectra were obtained at pressures up to 40 GPa at room temperature and up to 14 GPa at temperatures down to 80 K. For both lattice and intramolecular vibrational modes, a smooth evolution of spectral bands with pressure indicates that NO+NO3− forms a single phase over a broad range above 10 GPa, whereas marked changes, particularly evident in the Raman spectra at low temperature, indicate a phase transition occurs near 5 GPa. NO+NO3− could be recovered at atmospheric pressure and low temperature, persisting to 180 K. The Raman and IR spectroscopic data suggest that the NO+NO3− produced by laser heating of N2O followed by decompression may differ in structure or orientational order–disorder from that produced by autoionization ...

Several nitrogen oxide compounds transform to nitrosonium nitrate (NO+NO3−) under high pressure. In this study, NO+NO3− was synthesized by laser heating of N2O in a diamond-anvil cell and characterized by x-ray diffraction as a function of pressure at room temperature and low temperature. The unit-cell parameters were refined up to 32.2 GPa at 300 K, resulting in a denser structure than reported previously. The pressure-volume relations for NO+NO3− at 300 K were fitted to both Birch-Murnaghan and Vinet equations of state. The analysis indicates that NO+NO3− is denser than other nitrogen-oxygen assemblages, consistent with the conclusion that formation of the ionic species is driven by density rather than entropic effects. The low-temperature x-ray-diffraction data represent the first in situ measurements for this material, revealing consistent structural information and evolutions under pressure. These observations provide additional information on the stability relations and reaction diagram of N2O and N...

Raman spectra of zero pressure formed N2O4 solid layers are reported. Sample composition is extremely dependent upon deposition conditions. For ordered and pure solid N2O4(D2h), produced by slow NO2 deposition, temperature cycling over the range in which the solid is stable shows no significant spectral changes and does not result in autoionization, as argued in a previous Raman study. Fast and low temperature deposited layers are amorphous and multicomponent, showing bands of disordered and isomeric molecular N2O4 and of ionic NO+NO−3, nitrosonium nitrate. For nitrosonium nitrate, three solid modifications (two crystalline, one amorphous) can be characterized spectroscopically. In the amorphous phase, a light induced, temperature dependent, reversible transition between molecular and ionic nitrogen tetroxide is observed below 150 K. The paths leading to nitrosonium nitrate formation are examined.

Amorphous N2O4 solid was formed on predeposited oxygen or krypton layers. Evaporation of the underlying layer and redeposition of the inert impurities resulted in decomposition of the ionic nitrosonium nitrate clusters within the solid nitrogen tetroxide. Infrared features indicate NO+NO−3 decomposition to occur via molecular NONO3 , with NO2 monomers as products. Evaporation of the inert impurities and recooling restored the amorphous N2O4 from which NO+NO−3 was formed again.

Fourier transform infrared (FTIR) spectra of nitrogen dioxide layers deposited at various rates and substrate temperatures, are reported. Bands assignable to N2O4(D2h) (ordered and disordered layers), to O=N–O–NO2 ‘‘D’’ and ‘‘D’’’ isomers, to NO+NO−3 nitrosonium nitrate and to the NO2 monomer were observed. The relative amounts of species depends upon deposition conditions. Temperature cycling effects were followed up to 205 K. Solid N2O4(D2h) behaves like a normal, stable molecular solid, its disordered layer exhibiting small frequency shifts, but also being stable with respect to temperature cycling. The observation of NO+NO−3 bands is related to the existence of the D’ isomer and of monomeric NO2. Raman experiments overemphasize the NO+NO−3 form due to resonant enhancement.

The reactions of NO+ with H2O have been studied in a photoionization mass spectrometer. Nitrosonium ions produced by Kr resonance radiation at 10.03 eV react with water in a field free region. Products observed are NO(H2O)n+ (n=1, 2, 3) and H(H2O)n+ (n=1–5). Rate constants are calculated, heats of formation of hydrated NO+ are estimated and some evidence is presented which is consistent with a structure of NO(H2O)n+ where the waters are hydrogen bonded in a linear fashion rather than forming a solvation sphere.

Nitrosonium nitrate, NO+NO3−, a red solid, has been studied spectroscopically at temperatures ranging up to 205°K. Reproducible shifts of fundamental frequencies upon warming suggest two crystalline transformations between 79° and 205°K. The γ‐, β‐, and α‐phase have been observed under nonequilibrium conditions in the following temperature ranges, respectively: 79°—185°, 167°—187°, 167°—205°K. The fundamental frequencies of the constituent ions in the γ, β, and α phase are: ν(NO)+: 2215, 2271, 2251 cm−1; ν3: 1364, 1324, 1328 cm−1; ν2: 819, 827, 812 cm−1; ν4: 716, 716, 711 cm−1.

The question of whether the formation of the NO+NO−3 (nitrosonium nitrate), the ionic form of nitrogen dioxide, via the decomposition of the ON–O–NO2, ‘‘D’’’ isomer, is an inter‐ or intramolecular process, is addressed via temperature and concentration dependent FTIR studies of mixed films of N2O4 with CCl4. The process of nitrosonium nitrate production, both during deposition of disordered solid films of nitrogen dioxide and during their subsequent warming, is concluded to be intermolecular but not order dependent. A mechanism is tentatively suggested.

The autoionization of dinitrogen tetroxide to form nitrosonium nitrate in thin films at 150–200 K has been studied using infrared absorption spectroscopy. It is found that at these temperatures and low pressure the process is intramolecular, involving only one of two isomers of the nitrite form (ONONO2). (AIP)

Single stage enrichment factors α for the isotope exchange reaction of N15 between oxides of nitrogen and solutions of nitrosylsulphuric and nitrosylphosphoric acid have been determined. Single stage equilibration resulted in values of α that decrease from 1.046 for 1M to 1.013 for 10.2M sulphuric acid in the nitrosylsulphuric acid system, and from 1.042 for 4.7M to 1.005 for 14.8M phosphoric acid in the nitrosylphosphoric acid system.