Formation and phase distribution of nitric acid hydrates in the mole fraction range x<sub>HNO3</sub> &lt; 0.25: A combined XRD and IR study

Tizek, Heinz; Knözinger, Erich; Grothe, Hinrich

doi:10.1039/b310672a

Cited by 35 publications

(54 citation statements)

References 22 publications

(31 reference statements)

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“…The calculated vibrational frequencies and absorption intensities of both molecular structures are very close to each other. For example, the frequency of the asymmetric stretching of the O-N-O bonds in both NAT-1 and NAT-2 are 1323 and 1325 cm À1 , respectively, which is in very good agreement with the values measured by Tizek et al [9] and Koehler et al [10]. On the other hand, we have detected a 70 cm À1 difference between the peaks of the m NO-H .…”

Section: Molecular Structure Analysissupporting

confidence: 88%

“…Recent experimental measurements [9] have indicated that there are two molecular structures, the so-called a and b-NAT. The a-NAT is expected to form at 25 mol% HNO 3 and temperatures below 180 K [10] but when the temperature increases' the a-NAT structure starts to transform into the recognized b-NAT structure [9,10].…”

Section: Introductionmentioning

confidence: 99%

“…Experimental studies using the X-ray diffraction or infrared spectroscopy have identified the nitric acid monohydrates (NAM) [10], nitric acid dihydrates (NAD) [11,12] and the nitric acid trihydrates (NAT) [9,10].…”

Section: Introductionmentioning

confidence: 99%

“…The PSC Ia type consists of solid particles that are mainly composed of nitric acid hydrates with a negligible amount of sulfuric acid. The structures of these solid particles are difficult to classify due to the formation of stable and metastable hydrates [9]. The supercooled liquid of PSC Ib type consists of H 2 SO 4 /HNO 3 / H 2 O ternary solution [8,9], but in the PSC type II, H 2 O ice particles are the main constituent [8,9].…”

Section: Introductionmentioning

confidence: 99%

“…The a-NAT is expected to form at 25 mol% HNO 3 and temperatures below 180 K [10] but when the temperature increases' the a-NAT structure starts to transform into the recognized b-NAT structure [9,10]. In addition, Koehler et al [10] reported that this transformation is irreversible even in cases when the temperature of the system reverts to its previous value $180 K. This indicates that the b-NAT conformation is the most stable conformation and the one which is formed at high temperatures modification as described by Tizek et al [9]. To our knowledge earlier investigations have not identified the molecular structure of the a-NAT.…”

Section: Introductionmentioning

confidence: 99%

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Theoretical investigation of the coexistence of α and β-nitric acid trihydrates (NAT) molecular conformations

2006

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Section: Molecular Structure Analysissupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Theoretical investigation of the coexistence of α and β-nitric acid trihydrates (NAT) molecular conformations

2006

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The mid‐IR Absorption Cross Sections of α‐ and β‐NAT (HNO₃ · 3H₂O) in the range 170 to 185 K and of metastable NAD (HNO₃ · 2H₂O) in the range 172 to 182 K

Iannarelli

Rossi

2015

JGR Atmospheres

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Growth and Fourier transform infrared (FTIR) absorption in transmission of the title nitric acid hydrates have been performed in a stirred flow reactor (SFR) under tight control of the H2O and HNO3 deposition conditions affording a closed mass balance of the binary mixture. The gas and condensed phases have been simultaneously monitored using residual gas mass spectrometry and FTIR absorption spectroscopy, respectively. Barrierless nucleation of the metastable phases of both α‐NAT (nitric acid trihydrate) and NAD (nitric acid dihydrate) has been observed when HNO3 was admitted to the SFR in the presence of a macroscopic thin film of pure H2O ice of typically 1 µm thickness. The stable β‐NAT phase was spontaneously formed from the precursor α‐NAT phase through irreversible thermal rearrangement beginning at 185 K. This facile growth scheme of nitric acid hydrates requires the presence of H2O ice at thicknesses in excess of approximately hundred nanometers. Absolute absorption cross sections in the mid‐IR spectral range (700–4000 cm−1) of all three title compounds have been obtained after spectral subtraction of excess pure ice at temperatures characteristic of the upper troposphere/lower stratosphere. Prominent IR absorption frequencies correspond to the antisymmetric nitrate stretch vibration (ν3(NO3−)) in the range 1300 to 1420 cm−1 and the bands of hydrated protons in the range 1670 to 1850 cm−1 in addition to the antisymmetric O–H stretch vibration of bound H2O in the range 3380 to 3430 cm−1 for NAT.

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Comparing simulated PSC optical properties with CALIPSO observations during the 2010 Antarctic winter

et al. 2017

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We simulate polar stratospheric clouds (PSCs) during the Antarctic winter of 2010 using the Specified Dynamics version of the Whole Atmosphere Community Climate Model/Community Aerosol and Radiation Model for Atmospheres (SD‐WACCM/CARMA) model. The current PSC model contains microphysical schemes for supercooled ternary solutions (STS) and nitric acid trihydrate (NAT) particles, as well as a prognostic treatment for PSC ice particles and dehydration. Our simulations and CALIPSO satellite data suggest two major NAT particle formation mechanisms. The first mechanism is the nucleation of NAT from STS. Our model, with homogeneous nucleation rates of NAT from STS constrained by observations from the Arctic winter of 2010–2011, reproduces optical properties observed by CALIPSO over Antarctica in May and the timing of denitrification observed by the Microwave Limb Sounder within their uncertainties. On the other hand, the CALIPSO data indicate that our simulations are missing clouds containing small NAT particles with large number densities. We suggest these particles are most likely to form from ice clouds or STS in gravity waves, as found by previous investigations. The simulated cloud coverage agrees with the CALIPSO cloud coverage within a few percent on average with a correlation coefficient of 0.83. However, using the CALIPSO classification algorithm, simulated ice clouds often fall into Mix categories under the denitrified and dehydrated conditions. The model needs an improved ice microphysical representation, not only to allow ice particles to be a source of NAT but also to provide information on ice cloud particle number and size so that ice cloud optical properties can be more precisely calculated for comparison with CALIPSO data.

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Formation and phase distribution of nitric acid hydrates in the mole fraction range x_HNO3 < 0.25: A combined XRD and IR study

Cited by 35 publications

References 22 publications

Theoretical investigation of the coexistence of α and β-nitric acid trihydrates (NAT) molecular conformations

Theoretical investigation of the coexistence of α and β-nitric acid trihydrates (NAT) molecular conformations

The mid‐IR Absorption Cross Sections of α‐ and β‐NAT (HNO₃ · 3H₂O) in the range 170 to 185 K and of metastable NAD (HNO₃ · 2H₂O) in the range 172 to 182 K

Comparing simulated PSC optical properties with CALIPSO observations during the 2010 Antarctic winter

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Formation and phase distribution of nitric acid hydrates in the mole fraction range xHNO3 < 0.25: A combined XRD and IR study

Cited by 35 publications

References 22 publications

Theoretical investigation of the coexistence of α and β-nitric acid trihydrates (NAT) molecular conformations

Theoretical investigation of the coexistence of α and β-nitric acid trihydrates (NAT) molecular conformations

The mid‐IR Absorption Cross Sections of α‐ and β‐NAT (HNO3 · 3H2O) in the range 170 to 185 K and of metastable NAD (HNO3 · 2H2O) in the range 172 to 182 K

Comparing simulated PSC optical properties with CALIPSO observations during the 2010 Antarctic winter

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Formation and phase distribution of nitric acid hydrates in the mole fraction range x_HNO3 < 0.25: A combined XRD and IR study

The mid‐IR Absorption Cross Sections of α‐ and β‐NAT (HNO₃ · 3H₂O) in the range 170 to 185 K and of metastable NAD (HNO₃ · 2H₂O) in the range 172 to 182 K