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DOE OSTI2020

Materials Data on Ba3(ClO)2 by Materials Project

Ba3(OCl)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are three inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 4-coordinate geometry to four equivalent O2- and three equivalent Cl1- atoms. There are two shorter (2.60 Å) and two longer (2.62 Å) Ba–O bond lengths. There are one shorter (3.58 Å) and two longer (3.71 Å) Ba–Cl bond lengths. In the second Ba2+ site, Ba2+ is bonded in a 2-coordinate geometry to two equivalent O2- and three equivalent Cl1- atoms. Both Ba–O bond lengths are 2.39 Å. There are one shorter (3.24 Å) and two longer (3.84 Å) Ba–Cl bond lengths. In the third Ba2+ site, Ba2+ is bonded in a 6-coordinate geometry to two equivalent O2- and four Cl1- atoms. Both Ba–O bond lengths are 2.44 Å. There are a spread of Ba–Cl bond distances ranging from 3.18–3.61 Å. O2- is bonded to four Ba2+ atoms to form a mixture of corner and edge-sharing OBa4 tetrahedra. There are two inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a 7-coordinate geometry to seven Ba2+ atoms. In the second Cl1- site, Cl1- is bonded in a trigonal planar geometry to three equivalent Ba2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(ClO)2 by Materials Project

(BaO2Cl)2Cl2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional and consists of four hydrochloric acid molecules and one BaO2Cl framework. In the BaO2Cl framework, Ba is bonded in a 4-coordinate geometry to four O and three equivalent Cl atoms. There are a spread of Ba–O bond distances ranging from 2.72–2.81 Å. There are a spread of Ba–Cl bond distances ranging from 3.24–3.33 Å. There are two inequivalent O sites. In the first O site, O is bonded in a distorted bent 120 degrees geometry to two equivalent Ba and one Cl atom. The O–Cl bond length is 2.41 Å. In the second O site, O is bonded in a distorted bent 120 degrees geometry to two equivalent Ba atoms. Cl is bonded to three equivalent Ba and one O atom to form a mixture of distorted corner and edge-sharing ClBa3O trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiZn(ClO)3 by Materials Project

LiZn(OCl)3 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are four inequivalent Li sites. In the first Li site, Li is bonded in a 4-coordinate geometry to two O and two Cl atoms. There are one shorter (2.00 Å) and one longer (2.04 Å) Li–O bond lengths. There are one shorter (2.39 Å) and one longer (2.65 Å) Li–Cl bond lengths. In the second Li site, Li is bonded in a distorted rectangular see-saw-like geometry to two O and two Cl atoms. There are one shorter (2.02 Å) and one longer (2.05 Å) Li–O bond lengths. There are one shorter (2.46 Å) and one longer (2.54 Å) Li–Cl bond lengths. In the third Li site, Li is bonded in a 4-coordinate geometry to three O and one Cl atom. There are a spread of Li–O bond distances ranging from 1.90–2.23 Å. The Li–Cl bond length is 2.52 Å. In the fourth Li site, Li is bonded in a 4-coordinate geometry to two O and two Cl atoms. There is one shorter (1.90 Å) and one longer (1.99 Å) Li–O bond length. There are one shorter (2.45 Å) and one longer (2.71 Å) Li–Cl bond lengths. There are four inequivalent Zn sites. In the first Zn site, Zn is bonded to four Cl atoms to form corner-sharing ZnCl4 tetrahedra. There are a spread of Zn–Cl bond distances ranging from 2.25–2.37 Å. In the second Zn site, Zn is bonded to four Cl atoms to form corner-sharing ZnCl4 tetrahedra. There are a spread of Zn–Cl bond distances ranging from 2.25–2.35 Å. In the third Zn site, Zn is bonded to four Cl atoms to form distorted corner-sharing ZnCl4 tetrahedra. There are a spread of Zn–Cl bond distances ranging from 2.23–2.41 Å. In the fourth Zn site, Zn is bonded to four Cl atoms to form corner-sharing ZnCl4 tetrahedra. There are a spread of Zn–Cl bond distances ranging from 2.18–2.48 Å. There are twelve inequivalent O sites. In the first O site, O is bonded in a bent 120 degrees geometry to two O atoms. There is one shorter (1.27 Å) and one longer (1.37 Å) O–O bond length. In the second O site, O is bonded in a distorted trigonal planar geometry to two Li and one O atom. The O–O bond length is 1.39 Å. In the third O site, O is bonded in a single-bond geometry to one O atom. The O–O bond length is 1.23 Å. In the fourth O site, O is bonded in a distorted trigonal planar geometry to two Li and one O atom. The O–O bond length is 1.38 Å. In the fifth O site, O is bonded in a distorted bent 120 degrees geometry to one O and one Cl atom. The O–Cl bond length is 2.42 Å. In the sixth O site, O is bonded in a bent 120 degrees geometry to one O and one Cl atom. The O–O bond length is 1.27 Å. The O–Cl bond length is 2.34 Å. In the seventh O site, O is bonded in a distorted bent 120 degrees geometry to one Li and one O atom. In the eighth O site, O is bonded in a bent 120 degrees geometry to two O atoms. The O–O bond length is 1.27 Å. In the ninth O site, O is bonded in a distorted trigonal non-coplanar geometry to two Li and one Cl atom. The O–Cl bond length is 1.66 Å. In the tenth O site, O is bonded in a distorted single-bond geometry to one O atom. In the eleventh O site, O is bonded in a distorted trigonal planar geometry to two Li and one O atom. In the twelfth O site, O is bonded in a bent 120 degrees geometry to two O atoms. There are twelve inequivalent Cl sites. In the first Cl site, Cl is bonded in a bent 120 degrees geometry to two Zn atoms. In the second Cl site, Cl is bonded in a bent 120 degrees geometry to two Zn atoms. In the third Cl site, Cl is bonded in a bent 120 degrees geometry to two Zn atoms. In the fourth Cl site, Cl is bonded in a distorted T-shaped geometry to one Li and two Zn atoms. In the fifth Cl site, Cl is bonded in an L-shaped geometry to one Li and one Zn atom. In the sixth Cl site, Cl is bonded in a distorted L-shaped geometry to one Zn and one O atom. In the seventh Cl site, Cl is bonded in a distorted trigonal non-coplanar geometry to two Li and one Zn atom. In the eighth Cl site, Cl is bonded in a single-bond geometry to one Zn and one O atom. In the ninth Cl site, Cl is bonded in a distorted L-shaped geometry to one Zn and one O atom. In the tenth Cl site, Cl is bonded in a single-bond geometry to one Zn atom. In the eleventh Cl site, Cl is bonded in a distorted trigonal pyramidal geometry to three Li and one Zn atom. In the twelfth Cl site, Cl is bonded in a single-bond geometry to one Zn atom.

36 MATERIALS SCIENCE↗
NASA NTRS1989

Indicators of transport and vertical motion from correlations between in situ measurements in the Airborne Antarctic Ozone Experiment

Analysis of small-scale structure in the in situ measurements made from the ER-2 during the Airborne Antarctic Ozone Experiment shows the existence of a region at the boundary of the chemiclly perturbed region where the mixing ratios and small-scale structure of trace gases are influenced by transport across the boundary. This transition region is characterized by horizontal interchange and vertical layering of air parcels from within and outside of the chemically perturbed region and negative small-scale correlations between ClO and ozone. The horizontal transport in this region creates large surface areas between dissimilar air masses, providing the potential for substantial mixing. Correlations between ClO and O3 show that the transition region extends to 2-4 deg of latitude to either side of the boundary of the chemically perturbed region. A + or - 4-deg-wide transition region would contain nearly as much air as the chemically perturbed region proper. Analysis of water vapor and nitrous oxide data suggests that diabatic descent is associated with dehydration. This could be caused by strong radiative cooling of those polar stratospheric clouds in which enough water condenses for the particles to fall and dehydrate the air.

Murphy, D. M.↗
NASA NTRS1988

Chemistry of the CO dimer at low temperatures

Researchers conducted a series of experiments on the chlorine-catalyzed photodecomposition of O sub 3 both in the gas and in inert solvents such as CF sub 4 and CO sub 2 in the temperature range about 190 to 225 K. The liquid medium was chosen in order to minimize possible surface loss of long-lived ClO dimer, and to aid in the stabilization of transient excited intermediates. The mechanism of dimer formation was as follows: (1) Cl sub 2 + hv yields Cl + Cl; (2) Cl + O sub 3 yields ClO + O sub 2; (3) ClO + ClO yields Cl sub 2 O sub 2. The experiments were done in cooled low temperature cells, with irradiation from an Osram high pressure mercury arc, filtered to remove radiation below 325 nm. Spectral analysis was by means of a Cary Model 2200 UV spectrometer. The principal objectives were: (1) to determine the lifetime of the dimer as a function of temperature; (2) to observe spectral changes in the mixtures which could be attributed to dimer or related products; and (3) to observe chemical or photochemical reactions of the dimer.

Demore, W. B.↗
NASA NTRS1988

Small scale structure and mixing at the edge of the Antarctic vortex

Small scale correlations and patterns in the chemical tracers measured from the NASA ER-2 aircraft in the 1987 AAOE campaign can be used to investigate the structure of the edge of the polar vortex and the chemically perturbed region within it. Examples of several types of transport processes can be found in the data. Since ClO and O3 have similar vertical gradients and opposite horizontal gradients near the chemically perturbed region, the correlation between ClO and O3 can be used to study the extent of horizontal transport at the edge of the chemically perturbed region. Horizontal transport dominates the correlation for a latitude band up to 4 degrees on each side of the boundary. This implies a transition zone containing a substantial fraction of the mass of the total polar vortex. Similar horizontal transport can be seen in other tracers as well. It has not been possible to distinguish reversible transport from irreversible mixing. One manifestation of the horizontal transport is that the edge of the chemically perturbed region is often layered rather than a vertical curtain. This can be seen from the frequent reversed vertical gradients of NO2, caused by air with high NO2 overlapping layers with lower mixing ratios. Water and NO2 are positively correlated within the chemically perturbed region. This is the opposite sign to the correlation in the unperturbed stratosphere. The extent of the positive correlation is too great to be attributed solely to horizontal mixing. Instead, it is hypothesized that dehydration and descent are closely connected on a small scale, possibly due to radiative cooling of the clouds that also cause ice to fall to lower altitudes.

Murphy, D. M.↗
NASA NTRS1996

Southern Hemisphere In Situ Observations of OH, HO2, CIO and BrO from the ER-2 Aircraft for the 1994 ASHOE Mission

A summary of the first order scientific conclusions that emerged from the research done under this grant are as follows: (1) For the first time, the concentration of the key hydrogen and halogen radicals OH, H02, ClO and BrO were determined on a global scale extending from the arctic circle to the antarctic circle, over the altitude domain of the ER-2. That domain extends from 15-20 km altitude, covering a critical part of the lower stratosphere; (2) Simultaneous, in situ measurements of the concentrations of OH, H02, ClO, BrO, NO and NO2 demonstrate the predominance of odd-hydrogen and halogen free radical catalysis in determining the rate of removal of ozone in the lower stratosphere over the complete ASHOE mission. This extends to the global scale the "first look" data obtained during the NASA Stratospheric Photochemistry and Dynamics Experiment (SPADE), executed out of Ames Research Center in June 1993. This represents a major rearrangement of our understanding with respect to the hierarchy of dominant catalytic cycles controlling ozone loss in the lower stratosphere. For the past twenty years, it has been assumed that nitrogen radicals dominate the destruction rate of ozone in the lower stratosphere; (3) Throughout the altitude and latitude range covered by ASHOE, it was determined that a single catalytic cycle, HO2 + O3 yields OH + 2O2, accounted for one half of the total O3 removal in this region of the atmosphere. Halogen radical catalytic cycles were found to account for one third of the ozone loss, and nitrogen radicals were found to account for 20% of the loss; (4) Simultaneous observations of the full complement of radicals, tracers, ozone, and water vapor during ASHOE demonstrated quantitatively the coupling that exists between the rate limiting radicals and other reactive species in the photochemical reaction network. Specifically, the concentrations of ClO and HO2 are inversely correlated with the concentration of NOx. This carries the implication that the NOx effluent from the proposed High Speed Civil Transport may be less destructive to stratospheric ozone than had previously been thought. ASHOE brought this conclusion forward for the first time on a global basis; and (5) The density of BrO was measured on a global scale during ASHOE in the lower stratosphere. It was found that bromine is responsible for 55-65% of the local rate of catalytic destruction of ozone by reactions involving bromine and chlorine. Normalizing calculated loss rates to total available inorganic bromine and chlorine explicitly demonstrates that bromine is 60-80 times more efficient than chlorine in removing ozone in the lower stratosphere. An inferred value of total inorganic bromine is in excellent agreement with measurements of their source species, organic bromine compounds in the troposphere.

Anderson, James G.↗
NASA NTRS2011

Direct EPP Affects on the Middle Atmosphere

Energetic precipitating particles (EPPs) can cause significant direct constituent changes in the mesosphere and stratosphere (middle atmosphere) during certain periods. Both protons and electrons can influence the polar middle atmosphere through ionization and dissociation processes. EPPs can enhance HOx (H, OH, HO2) through the formation of positive ions followed by complex ion chemistry and NOx (N, NO, NO2) through the dissociation of molecular nitrogen. The HOx increases result in direct ozone destruction in the mesosphere and upper stratosphere via several catalytic loss cycles. Such middle atmospheric HOx-caused ozone loss is rather short-lived due to the relatively short lifetime (hours) of the HOx constituents. The NOx family has a considerably longer lifetime than the HOx family and can also lead to catalytic ozone destruction. EPP-caused enhancements of the NOx family can affect ozone directly, if produced in the stratosphere. Ozone decreases from the EPPs lead to a reduction in atmospheric heating and, subsequent atmospheric cooling. Conversely, EPPs can cause direct atmospheric heating through Joule heating. Measured HOx constituents OH and HO2 showed increases due to solar protons. Observed NOx constituents NO and NO2 were enhanced due to both solar protons and precipitating electrons. Other hydrogen- and nitrogen-ocntaining constituents were also measured to be directly influenced by EPPs, including N2O, HNO3, HO2NO2, N2OS, H2O2, ClONO2, HCl, and HOCl. Observed constituents ClO and CO were directly affected by EPPs as well. Many measurements indicated significant direct ozone decreases. A significant number of satellites housed instruments, which observed direct EPP-caused atmospheric effects, including Nimbus 4 (BUV), Nimbus 7 (SBUV), several NOAA platforms (SBUV/2), SME, UARS (HALOE, CLAES), SCISAT-1 (ACE-FTS), Odin (OSIRIS), Envisat-l (GOMOS, MIPAS, SCIAMACHY), and Aura (MLS). Measurements by rockets and ground-based radar also indicated EPP direct impacts. Atmospheric models have been used with some success in predicting the direct EPP impacts on the mesosphere and stratosphere. A review of the observed direct effects of EPP on the middle atmosphere will be given in this presentation.

Jackman, Charles H.↗
NASA NTRS1988

Chemistry of OClO in the Antarctic stratosphere - Implications for bromine

Previous observations of OClO over the Antarctic obtained in 1986 are used to constrain the stratospheric abundance of bromine. The observed diurnal variation is consistent with the production of OClO via the reaction of ClO with BrO if the branching ratio to the BrCl channel is between 3.5 and 14 percent. Otherwise, an additional source in twilight is indicated. The present results suggest a stratospheric bromine concentration of 16 + or - 4 pptv, a value which is consistent with independent measurements.

Salawitch, Ross J.↗
NASA NTRS1990

Description of SAFIRE for ISES

The SAFIRE (Spectroscopy of the Atmosphere using Far Infrared Emission) is a limb emission experiment using a far-IR Fourier transform spectrometer (FTS) and a mid-IR broadband multispectral radiometer covering the range 80 to 1600/cm. The purpose of this experiment is to obtain vertical distributions of temperature and key constituents of O(y), HO(y), NO(y), ClO(y), and BrO(y) families in the stratosphere, mesosphere, and thermosphere. The spectral channels and gases within each channel are summarized. The instrument includes a 48 element (6 x 8) Ge:GA detector array operating at 4 K in the far-IR and a 105 element (7 x 15) HgCdTe array operating at 80 K in the mid-IR. The SAFIRE uses four different scan modes for vertical coverage and resolution to address various scientific requirements. The SAFIRE data reduction will start with the retrieval of temperature profile as a function of pressure using two CO2 channel data. Constituent distributions then are obtained from other channel data using the retrieved temperature profile. The SAFIRE measurements are limited to the region above the tropopause because of radiance saturation by H2O and clouds. The computational capability necessary to process at the instrument data rate is estimated to be 19 MFLOPS for FTS data and 0.02 MFLOPS for radiometer data. It seems, therefore, that the real-time applications of SAFIRE data using an onboard processing device is not feasible. Although a temperature anomaly may be detected from the two CO2 radiometer channels using an onboard processor for the stratosphere, it is not possible to distinguish between CO2 outflux and temperature anomaly. Temperature anomaly does not, therefore, offer tropospheric information useful for real-time application.

Park, Jae H.↗
DOE OSTI2020

Materials Data on Ba3Bi(ClO)3 by Materials Project

Ba3Bi(OCl)3 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 8-coordinate geometry to three O2- and five Cl1- atoms. There are a spread of Ba–O bond distances ranging from 2.60–2.76 Å. There are a spread of Ba–Cl bond distances ranging from 3.24–3.61 Å. In the second Ba2+ site, Ba2+ is bonded in a 7-coordinate geometry to three O2- and four Cl1- atoms. There are one shorter (2.62 Å) and two longer (2.69 Å) Ba–O bond lengths. There are a spread of Ba–Cl bond distances ranging from 3.14–3.40 Å. Bi3+ is bonded in a distorted T-shaped geometry to three O2- atoms. There are one shorter (2.10 Å) and two longer (2.12 Å) Bi–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to three Ba2+ and one Bi3+ atom to form a mixture of distorted edge and corner-sharing OBa3Bi tetrahedra. In the second O2- site, O2- is bonded to three Ba2+ and one Bi3+ atom to form a mixture of distorted edge and corner-sharing OBa3Bi tetrahedra. There are two inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a 4-coordinate geometry to four Ba2+ atoms. In the second Cl1- site, Cl1- is bonded in a 6-coordinate geometry to six Ba2+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1989

In situ observations of BrO over Antarctica - ER-2 aircraft results from 54 deg S to 72 deg S latitude

Bromine monoxide was observed in situ during nine flights of the NASA ER-2 aircraft from Punta Arenas, Chile (54 deg S latitude), to 72 deg S latitude over the Palmer Peninsula, Antarctica. The first flight for the BrO detection system was on August 28. The distribution of BrO inside the chemically perturbed region defined by greatly elevated ClO abundances was different from that found just outside. Inside, the BrO mixing ratio was 6.1 + or - 1.1 pptv above the 440 K potential temperature surface, 4.7 + or - 2.0 pptv between the 400 and 440 K surfaces, and less than 4 pptv below the 400 K surface. At high latitudes outside the chemically perturbed region, the BrO mixing ratio was 5.4 + or - 1.4 pptv near the 450 K surface, but decreased to 2.9 + or - 1.2 pptv at the 420 K surface. The abundance of BrO showed no discernible temporal trend during the course of the nine flights. Away from the south polar region, at latitudes between 47 deg S and 37 deg N and potential temperatures between 435 and 500 K (18.5- to 20.7-km altitude), the BrO mixing ratio was 0.5-3.0 pptv.

Brune, W. H.↗
NASA NTRS1977

Rate constant for formation of chlorine nitrate by the reaction ClO + NO2 + M

The pseudo-first-order decay of ClO in a large excess of NO2 was monitored in a discharge flow/mass-spectrometer apparatus in order to measure the rate constant of the reaction ClO + NO2 + M yields ClONO2 + M for M = He, Ar, and N2 over the temperature range from 248 to 417 K. Numerical results are given for He at 248, 299, 360, and 417 K (1 to 9 torr); for Ar at 298 K (1 to 4 torr); and for N2 at 299, 360, and 417 K (1 to 6 torr). Systematic errors are estimated, and identification of the reaction product is discussed. The results obtained are shown to be in excellent agreement with other recent measurements of the same rate constant.

Leu, M. T.↗
DOE OSTI2020

Materials Data on CsMoS(ClO)2 by Materials Project

CsMoS(OCl)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Cs1+ sites. In the first Cs1+ site, Cs1+ is bonded in a 1-coordinate geometry to one O2- and four Cl1- atoms. The Cs–O bond length is 3.01 Å. There are a spread of Cs–Cl bond distances ranging from 3.35–3.71 Å. In the second Cs1+ site, Cs1+ is bonded in a 6-coordinate geometry to three O2- and three Cl1- atoms. There are a spread of Cs–O bond distances ranging from 3.08–3.73 Å. There are a spread of Cs–Cl bond distances ranging from 3.55–3.76 Å. There are two inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded in a 2-coordinate geometry to one S1-, two O2-, and two Cl1- atoms. The Mo–S bond length is 2.32 Å. There is one shorter (1.73 Å) and one longer (1.75 Å) Mo–O bond length. There are one shorter (2.33 Å) and one longer (2.83 Å) Mo–Cl bond lengths. In the second Mo6+ site, Mo6+ is bonded in a 1-coordinate geometry to two S1-, two O2-, and two Cl1- atoms. There are one shorter (2.44 Å) and one longer (2.49 Å) Mo–S bond lengths. There is one shorter (1.73 Å) and one longer (2.25 Å) Mo–O bond length. There are one shorter (2.39 Å) and one longer (2.47 Å) Mo–Cl bond lengths. There are two inequivalent S1- sites. In the first S1- site, S1- is bonded in a distorted single-bond geometry to one Mo6+ and one O2- atom. The S–O bond length is 1.58 Å. In the second S1- site, S1- is bonded in a distorted water-like geometry to two Mo6+ atoms. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one Mo6+ and one S1- atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to one Cs1+, one Mo6+, and one Cl1- atom. The O–Cl bond length is 3.02 Å. In the third O2- site, O2- is bonded in a distorted single-bond geometry to one Cs1+, one Mo6+, and one Cl1- atom. The O–Cl bond length is 3.04 Å. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Cs1+ and one Mo6+ atom. There are four inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a 1-coordinate geometry to two Cs1+ and one Mo6+ atom. In the second Cl1- site, Cl1- is bonded in a single-bond geometry to one Mo6+ atom. In the third Cl1- site, Cl1- is bonded in a 4-coordinate geometry to three Cs1+, one Mo6+, and two O2- atoms. In the fourth Cl1- site, Cl1- is bonded in a 1-coordinate geometry to two Cs1+ and one Mo6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiFe2(ClO)2 by Materials Project

LiFe2(OCl)2 is Hausmannite-derived structured and crystallizes in the monoclinic P2/c space group. The structure is three-dimensional. there are three inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded to four equivalent Cl1- atoms to form distorted LiCl4 trigonal pyramids that share corners with six FeCl2O4 octahedra, an edgeedge with one FeCl2O4 octahedra, and edges with two equivalent LiCl4 trigonal pyramids. The corner-sharing octahedra tilt angles range from 7–80°. There are two shorter (2.28 Å) and two longer (2.47 Å) Li–Cl bond lengths. In the second Li1+ site, Li1+ is bonded to four Cl1- atoms to form distorted LiCl4 trigonal pyramids that share corners with six FeCl2O4 octahedra, an edgeedge with one FeCl2O4 octahedra, and edges with two equivalent LiCl4 trigonal pyramids. The corner-sharing octahedra tilt angles range from 5–80°. There are two shorter (2.28 Å) and two longer (2.54 Å) Li–Cl bond lengths. In the third Li1+ site, Li1+ is bonded to four Cl1- atoms to form distorted LiCl4 trigonal pyramids that share corners with six FeCl2O4 octahedra, an edgeedge with one FeCl2O4 octahedra, and edges with two equivalent LiCl4 trigonal pyramids. The corner-sharing octahedra tilt angles range from 7–76°. There are two shorter (2.25 Å) and two longer (2.44 Å) Li–Cl bond lengths. There are six inequivalent Fe+2.50+ sites. In the first Fe+2.50+ site, Fe+2.50+ is bonded to four O2- and two equivalent Cl1- atoms to form distorted FeCl2O4 octahedra that share corners with two equivalent FeCl2O4 octahedra, corners with four LiCl4 trigonal pyramids, and edges with six FeCl2O4 octahedra. The corner-sharing octahedral tilt angles are 18°. There is two shorter (1.98 Å) and two longer (2.00 Å) Fe–O bond length. Both Fe–Cl bond lengths are 2.71 Å. In the second Fe+2.50+ site, Fe+2.50+ is bonded to four O2- and two equivalent Cl1- atoms to form distorted FeCl2O4 octahedra that share corners with two equivalent FeCl2O4 octahedra, corners with two equivalent LiCl4 trigonal pyramids, edges with six FeCl2O4 octahedra, and an edgeedge with one LiCl4 trigonal pyramid. The corner-sharing octahedral tilt angles are 17°. There are two shorter (1.99 Å) and two longer (2.01 Å) Fe–O bond lengths. Both Fe–Cl bond lengths are 2.61 Å. In the third Fe+2.50+ site, Fe+2.50+ is bonded to four equivalent O2- and two equivalent Cl1- atoms to form distorted FeCl2O4 octahedra that share corners with two equivalent FeCl2O4 octahedra, corners with four LiCl4 trigonal pyramids, and edges with six FeCl2O4 octahedra. The corner-sharing octahedral tilt angles are 18°. There are two shorter (2.05 Å) and two longer (2.28 Å) Fe–O bond lengths. Both Fe–Cl bond lengths are 2.61 Å. In the fourth Fe+2.50+ site, Fe+2.50+ is bonded to four O2- and two equivalent Cl1- atoms to form distorted FeCl2O4 octahedra that share corners with two equivalent FeCl2O4 octahedra, corners with four equivalent LiCl4 trigonal pyramids, and edges with six FeCl2O4 octahedra. The corner-sharing octahedral tilt angles are 17°. There are two shorter (2.05 Å) and two longer (2.25 Å) Fe–O bond lengths. Both Fe–Cl bond lengths are 2.63 Å. In the fifth Fe+2.50+ site, Fe+2.50+ is bonded to four O2- and two equivalent Cl1- atoms to form distorted FeCl2O4 octahedra that share corners with two equivalent FeCl2O4 octahedra, corners with two equivalent LiCl4 trigonal pyramids, edges with six FeCl2O4 octahedra, and an edgeedge with one LiCl4 trigonal pyramid. The corner-sharing octahedral tilt angles are 18°. There are two shorter (2.06 Å) and two longer (2.27 Å) Fe–O bond lengths. Both Fe–Cl bond lengths are 2.56 Å. In the sixth Fe+2.50+ site, Fe+2.50+ is bonded to four equivalent O2- and two equivalent Cl1- atoms to form distorted FeCl2O4 octahedra that share corners with two equivalent FeCl2O4 octahedra, corners with two equivalent LiCl4 trigonal pyramids, edges with six FeCl2O4 octahedra, and an edgeedge with one LiCl4 trigonal pyramid. The corner-sharing octahedral tilt angles are 18°. All Fe–O bond lengths are 2.00 Å. Both Fe–Cl bond lengths are 2.60 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted see-saw-like geometry to four Fe+2.50+ atoms. In the second O2- site, O2- is bonded in a distorted see-saw-like geometry to four Fe+2.50+ atoms. In the third O2- site, O2- is bonded in a distorted see-saw-like geometry to four Fe+2.50+ atoms. There are three inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a distorted see-saw-like geometry to two equivalent Li1+ and two Fe+2.50+ atoms. In the second Cl1- site, Cl1- is bonded in a 4-coordinate geometry to two Li1+ and two Fe+2.50+ atoms. In the third Cl1- site, Cl1- is bonded in a distorted see-saw-like geometry to two Li1+ and two Fe+2.50+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1997

The Kinetic Nonequilibrium Processes in the Internal Flow and in the Plume of Subsonic and Supersonic Aircrafts

(1) Our results show that under combustion of thermal destruction products of n-C8H18, and other hydrocarbon fuels with air at the equivalent ratio -0.5 and less the chemical equilibrium is not realized at the exit plane of combustion chamber and in the gas turbine and nozzle for most of small components such as NO2, NO3, HNO, HNO2, HNO3, N(x)H(y), HO2, OH. The chemical equilibrium is not realized in the internal flow of ramjet hydrogen combustion engine too. So at the nozzle exit plane both of gas-turbine hydrocarbon combustion engine and of ramjet hydrogen combustion engine the relatively large values of concentration of such small components as NO3, HNO2, N2O, HNO3, HNO, NH, N2H, HO2, H2O2 may be realized. The exact definition of these component concentration as well as concentration of NO(x), OH, SO2, O, H, H2, H2O at the nozzle exit plane is very important for plume chemistry. (2) The results which were obtained for subsonic and hypersonic aircrafts indicate on the considerable change of the composition of the gas mixture along the plume. This change can be caused not only by the mixture of combustion products with the atmosphere air but by proceeding of whole complex of nonequilibrium photochemical reactions. The photodissociation processes begin to influence on the formation of the free atoms and radicals at flight altitude H greater than or equal to 18 km. Neglect of these processes can result in essential (up to 10(exp 4) times) mistakes of values gamma(sub OH), gamma(sub O), gamma(sub H), gamma(sub HSO3) and some products of CFC's disintegration. It was found that penetration of Cl-containing species from the atmosphere into the exhaust flow and its interaction with nitrogen oxides leads to essential increasing of the concentration of Cl, Cl2, ClO2, ClNO3, CH3Cl and sometimes HCl and the decreasing of ClO concentration by comparison with background values. The results of our analysis show that the plume aircraft with both hydrocarbon and hydrogen combustion engine may be source of various pollutant components such as HNO, HNO4,ClO2, CH3NO2, CH3NO3, CH2O, Cl, H2O2, but not only NO, NO2, HNO2, HNO3, N2O5, SO2, SO3, H2SO4 as it was supposed before.

Starik, Alexander M.↗
NASA NTRS2005

Sensitivity of Ozone to Bromine in the Lower Stratosphere

Measurements of BrO suggest that inorganic bromine (Br(sub y)) at and above the tropopause is 4 to 8 ppt greater than assumed in models used in past ozone trend assessment studies. This additional bromine is likely carried to the stratosphere by short-lived biogenic compounds and their decomposition products, including tropospheric BrO. Including this additional bromine in an ozone trend simulation increases the computed ozone depletion over the past approx.25 years, leading to better agreement between measured and modeled ozone trends. This additional Br(sub y) (assumed constant over time) causes more ozone depletion because associated BrO provides a reaction partner for ClO, which increases due to anthropogenic sources. Enhanced Br(sub y) causes photochemical loss of ozone below approx.14 km to change from being controlled by HO(sub x) catalytic cycles (primarily HO2+O3) to a situation where loss by the BrO+HO2 cycle is also important.

ozone trends↗
NASA NTRS1990

In situ measurements of BrO in the Arctic stratosphere

Mixing ratios of BrO have been measured in the Arctic lower statosphere with an instrument mounted on the NASA ER-2 aircraft. Observations from fourteen flights above the Arctic Circle in January and February of 1989 defined mixing ratios within the vortex of 4 + or - 2 parts per trillion by volume (pptv) at a potential temperature of 400 K, rising to 8 + or - 2 pptv at 470 K. These values are twice as large as values found at equivalent potential temperatures at lower latitudes, and are comparable to the mixing ratios found inside the antarctic polar vortex. Within the statistical uncertainty of the measurements, no BrO was observed in darkness at any time either inside or outside of the vortex, indicating that active bromine was sequestered in long-lived reservoirs, probably BrONO2 and BrCl. These measurements, in conjuction with measurements of ClO, demonstrate that the interaction of bromine and chlorine could represent a major sink for ozone in the presence of sunlight.

Toohey, D. W.↗