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1
Kurosaki, Kenji, und Shu-ichiro Inutsuka. „Giant Impact Events for Protoplanets: Energetics of Atmospheric Erosion by Head-on Collision“. Astrophysical Journal 954, Nr. 2 (01.09.2023): 196. http://dx.doi.org/10.3847/1538-4357/ace9ba.
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Abstract Numerous exoplanets with masses ranging from Earth to Neptune and radii larger than Earth have been found through observations. These planets possess atmospheres that range in mass fractions from 1% to 30%, reflecting the diversity of atmospheric mass fractions. Such diversities are supposed to be caused by differences in the formation processes or evolution. Here, we consider head-on giant impacts onto planets causing atmosphere losses in the later stage of their formation. We perform smoothed particle hydrodynamic simulations to study the impact-induced atmosphere loss of young super-Earths with 10%–30% initial atmospheric mass fractions. We find that the kinetic energy of the escaping atmosphere is almost proportional to the sum of the kinetic impact energy and self-gravitational energy released from the merged core. We derive the relationship between the kinetic impact energy and the escaping atmosphere mass. The giant impact events for planets of comparable masses are required in the final stage of the popular scenario of rocky planet formation. We show it results in a significant loss of the atmosphere, if the impact is a head-on collision with comparable masses. This latter fact provides a constraint on the formation scenario of rocky planets with substantial atmospheres.
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Helling, Christiane, und Aleksejs Fomins. „Modelling the formation of atmospheric dust in brown dwarfs and planetary atmospheres“. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 371, Nr. 1994 (13.07.2013): 20110581. http://dx.doi.org/10.1098/rsta.2011.0581.
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Atmospheric dust from volcanoes, sand storms and biogenic products provides condensation seeds for water cloud formation on the Earth. Extrasolar planetary objects such as brown dwarfs and extrasolar giant planets have no comparable sources of condensation seeds. Hence, understanding cloud formation and further its implications for the climate requires a modelling effort that includes the treatment of seed formation (nucleation), growth and evaporation, in addition to rain-out, mixing and gas-phase depletion. This paper discusses nucleation in the ultra-cool atmospheres of brown dwarfs and extrasolar giant planets whose chemical gas-phase composition differs largely from the terrestrial atmosphere. A kinetic model for atmospheric dust formation is described, which, in recent work, has become part of a cloud-formation model. For the first time, diffusive replenishment of the upper atmosphere is introduced as a source term into our model equations. This paper further aims to show how experimental and computational chemistry work links into our dust-formation model, which is driven by applications in extraterrestrial environments.
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Shematovich, Valery, Dmitry Bisikalo und Grigory Tsurikov. „Non-Thermal Nitric Oxide Formation in the Earth’s Polar Atmosphere“. Atmosphere 14, Nr. 7 (29.06.2023): 1092. http://dx.doi.org/10.3390/atmos14071092.
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Auroral events are the prominent manifestation of solar/stellar forcing on planetary atmospheres because they are closely related to the stellar energy deposition by and evolution of planetary atmospheres. A numerical kinetic Monte Carlo model was developed with the aim to calculate the steady-state energy distribution functions of suprathermal N(4S) atoms in the polar upper atmosphere formed due to the precipitation of high-energy auroral electrons in the N2-O2 atmospheres of rocky planets in solar and exosolar planetary systems. This model describes on the molecular level the collisions of suprathermal N(4S) atoms and atmospheric gas taking into account the stochastic nature of collisional scattering at high kinetic energies. It was found that the electron impact dissociation of N2 is an important source of suprathermal N atoms, significantly increasing the non-thermal production of nitric oxide in the auroral regions of the N2-O2 atmospheres of terrestrial-type planets.
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Ohno, Kazumasa, und Jonathan J. Fortney. „Nitrogen as a Tracer of Giant Planet Formation. I. A Universal Deep Adiabatic Profile and Semianalytical Predictions of Disequilibrium Ammonia Abundances in Warm Exoplanetary Atmospheres“. Astrophysical Journal 946, Nr. 1 (01.03.2023): 18. http://dx.doi.org/10.3847/1538-4357/acafed.
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Abstract A major motivation of spectroscopic observations of giant exoplanets is to unveil planet formation processes from atmospheric compositions. Several recent studies suggested that atmospheric nitrogen, like carbon and oxygen, can provide important constraints on planetary formation environments. Since nitrogen chemistry can be far from thermochemical equilibrium in warm atmospheres, we extensively investigate under what conditions, and with what assumptions, the observable NH3 abundances can diagnose an atmosphere’s bulk nitrogen abundance. In the first paper of this series, we investigate atmospheric T–P profiles across equilibrium temperature, surface gravity, intrinsic temperature, atmospheric metallicity, and C/O ratio using a 1D radiative–convective equilibrium model. Models with the same intrinsic temperature and surface gravity coincide with a shared “universal” adiabat in the deep atmosphere, across a wide equilibrium temperature range (250–1200 K), which is not seen in hotter or cooler models. We explain this behavior in terms of the classic “radiative zero solution” and then establish a semianalytical T–P profile of the deep atmospheres of warm exoplanets. This profile is then used to predict vertically quenched NH3 abundances. At solar metallicity, our results show that the quenched NH3 abundance only coincides with the bulk nitrogen abundance (within 10%) at low intrinsic temperature, corresponding to a planet with a sub-Jupiter mass (≲1 M J) and old age (≳1 Gyr). If a planet has a high-metallicity (≳10× solar) atmosphere, the quenched NH3 abundance significantly underestimates the bulk nitrogen abundance at almost all planetary masses and ages. We suggest modeling and observational strategies to improve the assessment of bulk nitrogen from NH3.
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Hands, Tom O., und R. Helled. „Super stellar abundances of alkali metals suggest significant migration for hot Jupiters“. Monthly Notices of the Royal Astronomical Society 509, Nr. 1 (18.10.2021): 894–902. http://dx.doi.org/10.1093/mnras/stab2967.
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ABSTRACT We investigate the origin of the measured overabundance of alkali metals in the atmospheres of hot gas giants, relative to both their host stars and their atmospheric water abundances. We show that formation exterior to the water snow line followed by inward disc-driven migration results in excess accretion of oxygen-poor, refractory-rich material from within the snow-line. This naturally leads to enrichment of alkali metals in the planetary atmosphere relative to the bulk composition of its host star but relative abundances of water that are similar to the stellar host. These relative abundances cannot be explained by in situ formation which places the refractory elements in the planetary deep interior rather than the atmosphere. We therefore suggest that the measured compositions of the atmospheres of hot Jupiters are consistent with significant migration for at least a subset of hot gas giants. Our model makes robust predictions about atmospheric composition that can be confirmed with future data from JWST and Ariel.
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Chowdhury, Sohini, Yadaiah Nirsanametla und Muralidhar Manapuram. „Investigation on keyhole mode fiber laser welding of SS 316 in a self-protected atmosphere“. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 233, Nr. 18 (19.07.2019): 6602–15. http://dx.doi.org/10.1177/0954406219864137.
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This work focuses on examining the influence of welding parameters under different welding atmospheres and evaluation of keyhole profile during fiber laser welding operation. The experiments are carried out in two different welding atmospheres, namely self-protected atmosphere of Ar gas and open atmospheric conditions. The effect of these two atmospheric conditions on weld profile formation and dimensions, and microstructural evolution for SS 316 plates are examined. In addition, the keyhole profile is evaluated by using a semi-analytical mathematical model, a point-by-point energy balance determination at the keyhole wall, which is mapped with experimentally measured weld macrographs for similar welding conditions. It has been determined that the weld quality is profound in the case of a self-protected atmosphere with respect to aspect ratio, weld defects, and microstructural characterization. Moreover, better weld bead profile and cleaner weld seam on the upper surface is determined in samples welded in a self-protected atmosphere.
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Helling, Christiane. „Exoplanet Clouds“. Annual Review of Earth and Planetary Sciences 47, Nr. 1 (30.05.2019): 583–606. http://dx.doi.org/10.1146/annurev-earth-053018-060401.
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Clouds, which are common features in Earth's atmosphere, form in atmospheres of planets that orbit other stars than our Sun, in so-called extrasolar planets or exoplanets. Exoplanet atmospheres can be chemically extremely rich. Exoplanet clouds are therefore composed of a mix of materials that changes throughout the atmosphere. They affect atmospheres through element depletion and through absorption and scattering; hence, they have a profound impact on an atmosphere's energy budget. While astronomical observations point us to the presence of extrasolar clouds and make first suggestions on particle size and material composition, we require fundamental and complex modeling work to merge the individual observations into a coherent picture. Part of this work includes developing an understanding of cloud formation in nonterrestrial environments. ▪ Exoplanet atmospheres exhibit a wide chemical diversity that enables the formation of mineral clouds in contrast to the predominant water clouds on Earth. ▪ Clouds consume elements, causing specific atoms and molecules to drop in abundance. Transport processes such as gravitational settling or advection delocalize this process. ▪ Extrasolar planets can have extreme weather conditions where day- and nightside temperatures vary hugely. This affects cloud formation, and hence the cloud coverage and atmosphere's appearance can change dramatically. ▪ Dynamic extrasolar clouds develop intracloud lightning, and electric circuits may occur on more local, smaller scales in giant exoplanets compared to smaller, Earth-like planets with less dramatic hydrodynamics.
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Berndt, Torsten, Jing Chen, Eva R. Kjærgaard, Kristian H. Møller, Andreas Tilgner, Erik H. Hoffmann, Hartmut Herrmann, John D. Crounse, Paul O. Wennberg und Henrik G. Kjaergaard. „Hydrotrioxide (ROOOH) formation in the atmosphere“. Science 376, Nr. 6596 (27.05.2022): 979–82. http://dx.doi.org/10.1126/science.abn6012.
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Organic hydrotrioxides (ROOOH) are known to be strong oxidants used in organic synthesis. Previously, it has been speculated that they are formed in the atmosphere through the gas-phase reaction of organic peroxy radicals (RO 2 ) with hydroxyl radicals (OH). Here, we report direct observation of ROOOH formation from several atmospherically relevant RO 2 radicals. Kinetic analysis confirmed rapid RO 2 + OH reactions forming ROOOH, with rate coefficients close to the collision limit. For the OH-initiated degradation of isoprene, global modeling predicts molar hydrotrioxide formation yields of up to 1%, which represents an annual ROOOH formation of about 10 million metric tons. The atmospheric lifetime of ROOOH is estimated to be minutes to hours. Hydrotrioxides represent a previously omitted substance class in the atmosphere, the impact of which needs to be examined.
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Ohno, Kazumasa, und Takahiro Ueda. „Jupiter’s “cold” formation in the protosolar disk shadow“. Astronomy & Astrophysics 651 (Juli 2021): L2. http://dx.doi.org/10.1051/0004-6361/202141169.
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Context. Atmospheric compositions offer valuable clues to planetary formation and evolution. Jupiter has been the most well-studied giant planet in terms of its atmosphere; however, the origin of the Jovian atmospheric composition remains a puzzle as the abundances of nitrogen and noble gases as high as those of other elements could only originate from extremely cold environments. Aims. We propose a novel idea for explaining the Jovian atmospheric composition: dust pileup at the H2O snow line casts a shadow and cools the Jupiter orbit so that N2 and noble gases can freeze. Planetesimals or a core formed in the shadowed region can enrich nitrogen and noble gases as much as other elements through their dissolution in the envelope. Methods. We compute the temperature structure of a shadowed protosolar disk with radiative transfer calculations. Then, we investigate the radial volatile distributions and predict the atmospheric composition of Jupiter with condensation calculations. Results. We find that the vicinity of the current Jupiter orbit, approximately 3 − 7 AU, could be as cold as ≲30 K if the small-dust surface density varies by a factor of ≳30 across the H2O snow line. According to previous grain growth simulations, this condition could be achieved by weak disk turbulence if silicate grains are more fragile than icy grains. The shadow can cause the condensation of most volatile substances, namely N2 and Ar. We demonstrate that the dissolution of shadowed solids can explain the elemental abundance patterns of the Jovian atmosphere even if proto-Jupiter was formed near Jupiter’s current orbit. Conclusions. The disk shadow may play a vital role in controlling atmospheric compositions. The effect of the shadow also impacts the interpretation of upcoming observations of exoplanetary atmospheres by JWST.
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Watanabe, Yasuto, und Kazumi Ozaki. „Relative Abundances of CO2, CO, and CH4 in Atmospheres of Earth-like Lifeless Planets“. Astrophysical Journal 961, Nr. 1 (01.01.2024): 1. http://dx.doi.org/10.3847/1538-4357/ad10a2.
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Abstract Carbon is an essential element for life on Earth, and the relative abundances of major carbon species (CO2, CO, and CH4) in the atmosphere exert fundamental controls on planetary climate and biogeochemistry. Here we employed a theoretical model of atmospheric chemistry to investigate diversity in the atmospheric abundances of CO2, CO, and CH4 on Earth-like lifeless planets orbiting Sun-like (F-, G-, and K-type) stars. We focused on the conditions for the formation of a CO-rich atmosphere, which would be favorable for the origin of life. Results demonstrated that elevated atmospheric CO2 levels trigger photochemical instability of the CO budget in the atmosphere (i.e., CO runaway) owing to enhanced CO2 photolysis relative to H2O photolysis. Higher volcanic outgassing fluxes of reduced C (CO and CH4) also tend to initiate CO runaway. Our systematic examinations revealed that anoxic atmospheres of Earth-like lifeless planets could be classified in the phase space of CH4/CO2 versus CO/CO2, where a distinct gap in atmospheric carbon chemistry is expected to be observed. Our findings indicate that the gap structure is a general feature of Earth-like lifeless planets with reducing atmospheres orbiting Sun-like (F-, G-, and K-type) stars.
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Heo, Ki-Young, und Kyung-Ja Ha. „A Coupled Model Study on the Formation and Dissipation of Sea Fogs“. Monthly Weather Review 138, Nr. 4 (01.04.2010): 1186–205. http://dx.doi.org/10.1175/2009mwr3100.1.
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Abstract This study examined the impact of air–sea coupling using a coupled atmosphere–ocean modeling system consisting of the Coupled Ocean–Atmosphere Mesoscale Prediction System as the atmospheric component and the Regional Ocean Modeling System as the oceanic component. Numerical experiments for advection and steam fog events were carried out to clarify the modulation of the formation and dissipation of sea fogs by the air–sea temperature difference (air temperature minus sea surface temperature) and the atmospheric stability. The coupled simulation showed that advection fog is obviously controlled by low-level atmospheric stability and downward latent heat flux with oceanic cooling through air–sea coupling. In particular, air–sea coupling stabilizes the low-level atmosphere at the dissipation stage, and then suppresses vertical mixing, which retards the dissipation of advection fog. In the case of a steam fog event, the upward turbulent heat fluxes are increased significantly from the formation time to the mature time. A decrease in sea surface temperature cools the low-level atmosphere, which increases the condensation rate and low-level atmospheric stability, eventually retarding the dissipation of steam fog.
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Jacobs, Bob, Jean-Michel Désert, Peter Gao, Caroline V. Morley, Jacob Arcangeli, Saugata Barat, Mark S. Marley et al. „Probing Reflection from Aerosols with the Near-infrared Dayside Spectrum of WASP-80b“. Astrophysical Journal Letters 956, Nr. 2 (01.10.2023): L43. http://dx.doi.org/10.3847/2041-8213/acfee9.
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Abstract The presence of aerosols is intimately linked to the global energy budget and the composition of a planet’s atmosphere. Their ability to reflect incoming light prevents energy from being deposited into the atmosphere, and they shape the spectra of exoplanets. We observed five near-infrared secondary eclipses of WASP-80b with the Wide Field Camera 3 (WFC3) aboard the Hubble Space Telescope to provide constraints on the presence and properties of atmospheric aerosols. We detect a broadband eclipse depth of 34 ± 10 ppm for WASP-80b. We detect a higher planetary flux than expected from thermal emission alone at 1.6σ, which hints toward the presence of reflecting aerosols on this planet’s dayside, indicating a geometric albedo of A g < 0.33 at 3σ. We paired the WFC3 data with Spitzer data and explored multiple atmospheric models with and without aerosols to interpret this spectrum. Albeit consistent with a clear dayside atmosphere, we found a slight preference for near-solar metallicities and for dayside clouds over hazes. We exclude soot haze formation rates higher than 10−10.7 g cm−2s−1 and tholin formation rates higher than 10−12.0 g cm−2s−1 at 3σ. We applied the same atmospheric models to a previously published WFC3/Spitzer transmission spectrum for this planet and found weak haze formation. A single soot haze formation rate best fits both the dayside and the transmission spectra simultaneously. However, we emphasize that no models provide satisfactory fits in terms of the chi-square of both spectra simultaneously, indicating longitudinal dissimilarity in the atmosphere’s aerosol composition.
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Kimura, Tadahiro, und Masahiro Ikoma. „Formation of aqua planets with water of nebular origin: effects of water enrichment on the structure and mass of captured atmospheres of terrestrial planets“. Monthly Notices of the Royal Astronomical Society 496, Nr. 3 (22.06.2020): 3755–66. http://dx.doi.org/10.1093/mnras/staa1778.
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ABSTRACT Recent detection of exoplanets with Earth-like insolation attracts growing interest in how common Earth-like aqua planets are beyond the Solar system. While terrestrial planets are often assumed to capture icy or water-rich planetesimals, a primordial atmosphere of nebular origin itself can produce water through oxidation of the atmospheric hydrogen with oxidizing minerals from incoming planetesimals or the magma ocean. Thermodynamically, normal oxygen buffers produce water comparable in mole number equal to or more than hydrogen. Thus, the primordial atmosphere would likely be highly enriched with water vapour; however, the primordial atmospheres have been always assumed to have the solar abundances. Here we integrate the 1D structure of such an enriched atmosphere of sub-Earths embedded in a protoplanetary disc around an M dwarf of 0.3$\, \mathrm{M}_\odot$ and investigate the effects of water enrichment on the atmospheric properties with focus on water amount. We find that the well-mixed highly enriched atmosphere is more massive by a few orders of magnitude than the solar-abundance atmosphere, and that even a Mars-mass planet can obtain water comparable to the present Earth’s oceans. Although close-in Mars-mass planets likely lose the captured water via disc dispersal and photoevaporation, these results suggest that there are more sub-Earths with Earth-like water contents than previously predicted. How much water terrestrial planets really obtain and retain against subsequent loss, however, depends on efficiencies of water production, mixing in the atmosphere and magma ocean, and photoevaporation, detailed investigation for which should be made in the future.
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Sinclair, Catriona A., Mark C. Wyatt, Alessandro Morbidelli und David Nesvorný. „Evolution of the Earth’s atmosphere during Late Veneer accretion“. Monthly Notices of the Royal Astronomical Society 499, Nr. 4 (16.10.2020): 5334–62. http://dx.doi.org/10.1093/mnras/staa3210.
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ABSTRACT Recent advances in our understanding of the dynamical history of the Solar system have altered the inferred bombardment history of the Earth during accretion of the Late Veneer, after the Moon-forming impact. We investigate how the bombardment by planetesimals left-over from the terrestrial planet region after terrestrial planet formation, as well as asteroids and comets, affects the evolution of Earth’s early atmosphere. We develop a new statistical code of stochastic bombardment for atmosphere evolution, combining prescriptions for atmosphere loss and volatile delivery derived from hydrodynamic simulations and theory with results from dynamical modelling of realistic populations of impactors. We find that for an initially Earth-like atmosphere, impacts cause moderate atmospheric erosion with stochastic delivery of large asteroids, giving substantial growth (× 10) in a few ${{\ \rm per\ cent}}$ of cases. The exact change in atmosphere mass is inherently stochastic and dependent on the dynamics of the left-over planetesimals. We also consider the dependence on unknowns including the impactor volatile content, finding that the atmosphere is typically completely stripped by especially dry left-over planetesimals ($\lt 0.02 ~ {{\ \rm per\ cent}}$ volatiles). Remarkably, for a wide range of initial atmosphere masses and compositions, the atmosphere converges towards similar final masses and compositions, i.e. initially low-mass atmospheres grow, whereas massive atmospheres deplete. While the final properties are sensitive to the assumed impactor properties, the resulting atmosphere mass is close to that of current Earth. The exception to this is that a large initial atmosphere cannot be eroded to the current mass unless the atmosphere was initially primordial in composition.
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Schaefer, Laura K., und Vivien Parmentier. „The Air Over There: Exploring Exoplanet Atmospheres“. Elements 17, Nr. 4 (01.08.2021): 257–63. http://dx.doi.org/10.2138/gselements.17.4.257.
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The atmospheric composition for a rocky exoplanet will depend strongly on the planet’s bulk composition and orbital position. Nontraditional gases may be present in the atmospheres of exceptionally hot planets. Atmospheres of more clement planets will depend on the abundance of volatiles acquired during planet formation and atmospheric removal processes, including escape, condensation, and reaction with the surface. To date, observations of exoplanet atmospheres have focused on giant planets, but future space-and ground-based observatories will revolutionize the precision and spectral resolution with which we can probe an exoplanet’s atmosphere. This article consolidates lessons learned from the study of giant planet atmospheres, and points to the observations and challenges on the horizon for terrestrial planets.
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Helling, Ch, und F. J. M. Rietmeijer. „Glittery clouds in exoplanetary atmospheres?“ International Journal of Astrobiology 8, Nr. 1 (Januar 2009): 3–8. http://dx.doi.org/10.1017/s1473550408004382.
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AbstractCloud formation modelling has entered astrophysics as a new field of research for planetary and brown dwarf atmospheres. Clouds are a chemically and physically very active component of an atmosphere since they determine the remaining gas phase and change the object's albedo depending on their material composition. The grains can also provide a surface where the molecular constituents for life can be physisorbed for possible pre-biotic evolution. This paper summarizes our model for the kinetic formation of dirty dust grains which make up the atmospheric clouds of extraterrestrial giant gas planets. We include seed formation, surface growth and evaporation, the gravitational settling that influences the dust formation, element depletion that determines the remaining gas phase abundances, and convective overshooting that is needed for a dust model to be applicable to hydrostatic atmosphere simulations. We demonstrate the evolution of the material composition of the cloud itself and the distribution of the grain sizes in the cloud layer, exemplary for a giant gas planet parameter combinations (Teff, log g). In general, substellar clouds are composed of small, dirty grains with a high silicate content at the cloud deck. They grow in size and gradually purify to iron/corundum grains when they move into denser and hotter atmospheric regions. Comparing these results with experimental data from condensation experiments leads to the conclusion that cloud grains that gravitationally settle in the atmosphere of a giant planet can easily change their lattice structure from the disordered amorphous state they are forming in, into the ordered lattice of a crystal.
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Parveg, A. S. M. Sazzad, Ramin Ordikhani-Seyedlar, Tejasvi Sharma, Scott K. Shaw und Albert Ratner. „A Recycling Pathway for Rare Earth Metals (REMs) from E-Waste through Co-Gasification with Biomass“. Energies 15, Nr. 23 (02.12.2022): 9141. http://dx.doi.org/10.3390/en15239141.
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This manuscript investigates an improvised gasification process for capturing and recycling rare earth metals (REMs) from consumer and industrial electronic wastes, often termed “e-waste”. The proposed procedure is based on the formation of coalesced and aggregated metal nodules on biochar surfaces through the gasification of e-waste mixed with gasifier feedstocks. A preliminary understanding of metal nodule formation based on different atmospheric conditions (inert, oxidizing, and oxidizing followed by reducing atmospheres) was examined in both pilot-scale gasifier and tube furnace experiments using iron powder mixed with corn. Iron powder is representative of the REM in the e-waste. Metal nodule sizes, morphology, and composition are analyzed and compared via scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray fluorescence spectroscopy (XRF) techniques. We conclude that sintering is the key mechanism responsible for metal nodule growth through metal particle coalescence and aggregation by migration and diffusion of metal particles on biochar surfaces at elevated temperatures. Oxidizing atmosphere followed by a reducing atmosphere facilitates larger metal nodule growth compared to only an inert or oxidizing atmosphere. Additionally, the effect of adding NaCl salt is investigated on lowering the metal nodules’ surface energy and enhancing both metal particle and metal nodule agglomeration characteristics. Salt addition facilitates spherical metal nodule formation without any significant effect on the nodule composition and localized formation of nodules.
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Helling, Christiane, und Paul B. Rimmer. „Lightning and charge processes in brown dwarf and exoplanet atmospheres“. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 377, Nr. 2154 (05.08.2019): 20180398. http://dx.doi.org/10.1098/rsta.2018.0398.
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The study of the composition of brown dwarf atmospheres helped to understand their formation and evolution. Similarly, the study of exoplanet atmospheres is expected to constrain their formation and evolutionary states. We use results from three-dimensional simulations, kinetic cloud formation and kinetic ion-neutral chemistry to investigate ionization processes that will affect their atmosphere chemistry: the dayside of super-hot Jupiters is dominated by atomic hydrogen, and not H 2 O. Such planetary atmospheres exhibit a substantial degree of thermal ionization and clouds only form on the nightside where lightning leaves chemical tracers (e.g. HCN) for possibly long enough to be detectable. External radiation may cause exoplanets to be enshrouded in a shell of highly ionized, H 3 + -forming gas and a weather-driven aurora may emerge. Brown dwarfs enable us to study the role of electron beams for the emergence of an extrasolar, weather system-driven aurora-like chemistry, and the effect of strong magnetic fields on cold atmospheric gases. Electron beams trigger the formation of H 3 + in the upper atmosphere of a brown dwarf (e.g. LSR-J1835), which may react with it to form hydronium, H 3 O + , as a longer lived chemical tracer. Brown dwarfs and super-hot gas giants may be excellent candidates to search for H 3 O + as an H 3 + product. This article is part of a discussion meeting issue ‘Advances in hydrogen molecular ions: H 3 + , H 5 + and beyond’.
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MIRABEL, P., A. SOROKIN und E. MARTIN. „AEROSOL FORMATION IN THE ATMOSPHERE“. Journal of Aerosol Science 32 (September 2001): 7–8. http://dx.doi.org/10.1016/s0021-8502(21)00013-6.
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Sedlmayr, E., und A. B. C. Patzer. „Grain formation and dynamical atmosphere“. EAS Publications Series 11 (2004): 51–66. http://dx.doi.org/10.1051/eas:2004003.
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Kravchenko, K., S. Van Eck, A. Chiavassa, A. Jorissen, B. Freytag und B. Plez. „Tomography of cool giant and supergiant star atmospheres“. Astronomy & Astrophysics 610 (Februar 2018): A29. http://dx.doi.org/10.1051/0004-6361/201731530.
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Context. Cool giant and supergiant star atmospheres are characterized by complex velocity fields originating from convection and pulsation processes which are not fully understood yet. The velocity fields impact the formation of spectral lines, which thus contain information on the dynamics of stellar atmospheres. Aim. The tomographic method allows to recover the distribution of the component of the velocity field projected on the line of sight at different optical depths in the stellar atmosphere. The computation of the contribution function to the line depression aims at correctly identifying the depth of formation of spectral lines in order to construct numerical masks probing spectral lines forming at different optical depths. Methods. The tomographic method is applied to one-dimensional (1D) model atmospheres and to a realistic three-dimensional (3D) radiative hydrodynamics simulation performed with CO5BOLD in order to compare their spectral line formation depths and velocity fields. Results. In 1D model atmospheres, each spectral line forms in a restricted range of optical depths. On the other hand, in 3D simulations, the line formation depths are spread in the atmosphere mainly because of temperature and density inhomogeneities. Comparison of cross-correlation function profiles obtained from 3D synthetic spectra with velocities from the 3D simulation shows that the tomographic method correctly recovers the distribution of the velocity component projected on the line of sight in the atmosphere.
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Kurosaki, Kenji, Yasunori Hori, Masahiro Ogihara und Masanobu Kunitomo. „Evolution of a Water-rich Atmosphere Formed by a Giant Impact on an Earth-sized Planet“. Astrophysical Journal 957, Nr. 2 (31.10.2023): 67. http://dx.doi.org/10.3847/1538-4357/acfe0a.
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Abstract The atmosphere of a terrestrial planet that is replenished with secondary gases should have accumulated hydrogen-rich gas from its protoplanetary disk. Although a giant impact blows off a large fraction of the primordial atmosphere of a terrestrial planet in the late formation stage, the remaining atmosphere can become water-rich via chemical reactions between hydrogen and vaporized core material. We find that a water-rich postimpact atmosphere forms when a basaltic or CI chondrite core is assumed. In contrast, little postimpact water is generated for an enstatite chondrite core. We investigate the X-ray- and UV-driven mass loss from an Earth-mass planet with an impact-induced multicomponent H2–He–H2O atmosphere for Gyr. We show that water is left in the atmosphere of an Earth-mass planet when the low flux of escaping hydrogen cannot drag water upward via collisions. For a water-dominated atmosphere to form, the atmospheric mass fraction of an Earth-mass planet with an oxidizing core after a giant impact must be less than a few times 0.1%. We also find that Earth-mass planets with water-dominated atmospheres can exist at semimajor axes ranging from a few times 0.1 au to a few au around a Sun-like star, depending on the mass-loss efficiency. Such planets are important targets for atmospheric characterization in the era of JWST. Our results indicate that efficient mixing between hydrogen and rocky components during giant impacts can play a role in the production of water in an Earth-mass planet.
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Jokinen, T., M. Sipilä, J. Kontkanen, V. Vakkari, P. Tisler, E. M. Duplissy, H. Junninen et al. „Ion-induced sulfuric acid–ammonia nucleation drives particle formation in coastal Antarctica“. Science Advances 4, Nr. 11 (November 2018): eaat9744. http://dx.doi.org/10.1126/sciadv.aat9744.
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Formation of new aerosol particles from trace gases is a major source of cloud condensation nuclei (CCN) in the global atmosphere, with potentially large effects on cloud optical properties and Earth’s radiative balance. Controlled laboratory experiments have resolved, in detail, the different nucleation pathways likely responsible for atmospheric new particle formation, yet very little is known from field studies about the molecular steps and compounds involved in different regions of the atmosphere. The scarcity of primary particle sources makes secondary aerosol formation particularly important in the Antarctic atmosphere. Here, we report on the observation of ion-induced nucleation of sulfuric acid and ammonia—a process experimentally investigated by the CERN CLOUD experiment—as a major source of secondary aerosol particles over coastal Antarctica. We further show that measured high sulfuric acid concentrations, exceeding 107 molecules cm−3, are sufficient to explain the observed new particle growth rates. Our findings show that ion-induced nucleation is the dominant particle formation mechanism, implying that galactic cosmic radiation plays a key role in new particle formation in the pristine Antarctic atmosphere.
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Autushka, M. I., A. V. Matveyev und S. A. Isachenko. „Recent data on radon entry into the human environment“. Doklady of the National Academy of Sciences of Belarus 65, Nr. 3 (16.07.2021): 355–60. http://dx.doi.org/10.29235/1561-8323-2021-65-3-355-360.
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Radon transported from the atmosphere to the earth’s surface is shown to have a significant role in the formation of its concentration levels in the lowest atmospheric layers. The amount of radon escaping from the atmosphere with sporadically occurred rainfalls is quantitatively comparable with the amounts emitted from the soil into the atmosphere. A stable dependence has been established between the radon concentration levels in the surface atmosphere and the air humidity
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Zhang, Yapeng, Ignas A. G. Snellen und Paul Mollière. „The 12CO/13CO isotopologue ratio of a young, isolated brown dwarf“. Astronomy & Astrophysics 656 (Dezember 2021): A76. http://dx.doi.org/10.1051/0004-6361/202141502.
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Context. Linking atmospheric characteristics of planets to their formation pathways is a central theme in the study of extrasolar planets. Although the 12C/13C isotope ratio shows little variation in the Solar System, the atmosphere of a super-Jupiter was recently shown to be rich in 13CO, possibly as a result of dominant ice accretion beyond the CO snow line during its formation. Carbon isotope ratios are therefore suggested to be a potential tracer of formation pathways of planets. Aims. In this work, we aim to measure the 12CO/13CO isotopologue ratio of a young, isolated brown dwarf. While the general atmospheric characteristics of young, low-mass brown dwarfs are expected to be very similar to those of super-Jupiters, their formation pathways may be different, leading to distinct isotopologue ratios. In addition, such objects allow high-dispersion spectroscopy at high signal-to-noise ratios. Methods. We analysed archival K-band spectra of the L dwarf 2MASS J03552337+1133437 taken with NIRSPEC at the Keck telescope. A free retrieval analysis was applied to the data using the radiative transfer code petitRADTRANS coupled with the nested sampling tool PyMultiNest to determine the isotopologue ratio 12CO/13CO in its atmosphere. Results. The isotopologue 13CO is detected in the atmosphere through the cross-correlation method at a signal-to-noise of ~8.4. The detection significance is determined to be ~9.5σ using a Bayesian model comparison between two retrieval models (including or excluding 13CO). We retrieve an isotopologue 12CO/13CO ratio of 97−18+25 (90% uncertainty), marginally higher than the local interstellar standard. Its C/O ratio of ~0.56 is consistent with the solar value. Conclusions. Although only one super-Jupiter and one brown dwarf now have a measured 12CO/13CO ratio, it is intriguing that they are different, possibly hinting to distinct formation pathways. Regardless of spectroscopic similarities, isolated brown dwarfs may experience a top-down formation via gravitational collapse, which resembles star formation, while giant exoplanets favourably form through core accretion, which potentially alters isotopologue ratios in their atmospheres depending on the material they accrete from protoplanetary disks. This further emphasises atmospheric carbon isotopologue ratio as a tracer of the formation history of exoplanets. In the future, analyses such as those presented here should be conducted on a wide range of exoplanets using medium-to-high-resolution spectroscopy to further assess planet formation processes.
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Gusev, A. A., E. G. Avvakumov und O. B. Vinokurova. „Synthesis of Ti4O7 magneli phase using mechanical activation“. Science of Sintering 35, Nr. 3 (2003): 141–45. http://dx.doi.org/10.2298/sos0303141g.
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The processes of phase formation by heating of a mechanically activated mixture of Ti + TiO2 in different atmospheres (air, argon, hydrogen) were investigated. The Ti4O7 compound was obtained by annealing of the mixture in hydrogen atmosphere in the interval of temperatures of 900-1200?C, the Ti2O3 oxide formed at 800?C in argon atmosphere and TiO2 formed in air atmosphere Conductivity and morphology of Ti4O7 samples obtained in hydrogen were studied.
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Zhen, Shaosong, Min Luo, Yang Shao, Diandou Xu und Lingling Ma. „Application of Stable Isotope Techniques in Tracing the Sources of Atmospheric NOX and Nitrate“. Processes 10, Nr. 12 (30.11.2022): 2549. http://dx.doi.org/10.3390/pr10122549.
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Nitrate is an important component of PM2.5, and its dry deposition and wet deposition can have an impact on ecosystems. Nitrate in the atmosphere is mainly transformed by nitrogen oxides (NOX = NO + NO2) through a number of photochemical processes. For effective management of the atmosphere’s environment, it is crucial to understand the sources of atmospheric NOX and the processes that produce atmospheric nitrate. The stable isotope method is an effective analytical method for exploring the sources of NO3− in the atmosphere. This study discusses the range and causes of δ15N data from various sources of NOX emissions, provides the concepts of stable isotope techniques applied to NOX traceability, and introduces the use of Bayesian mixture models for the investigation of NOX sources. The combined application of δ15N and δ18O to determine the pathways of nitrate formation is summarized, and the contribution of Δ17O to the atmospheric nitrate formation pathway and the progress of combining Δ17O simulations to reveal the atmospheric oxidation characteristics of different regions are discussed, respectively. This paper highlights the application results and development trend of stable isotope techniques in nitrate traceability, discusses the advantages and disadvantages of stable isotope techniques in atmospheric NOX traceability, and looks forward to its future application in atmospheric nitrate pollution. The research results could provide data support for regional air pollution control measures.
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Gabor, Dan, Emilian Ghicioi, Mihaela Părăian, Niculina Vătavu, Florin Adrian Păun und Mihai Popa. „Sensitivity to ignition by electrostatic discharge of explosive dust / air“. MATEC Web of Conferences 290 (2019): 12011. http://dx.doi.org/10.1051/matecconf/201929012011.
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In industrial sectors that use, process, transport or store, substances such as combustible dusts could exist some workplaces with explosion hazard due to the possibility of dust/air explosive formation and ignition, both inside the installations and in the surrounding atmosphere. Methods and means of protection aim to prevent the development of explosive atmospheres, followed by preventing the occurrence of ignition sources and then limiting the effects of explosions. To assess the risk of ignition of the explosive atmosphere, there must be known first of all, the explosive atmosphere’s sensitivity to ignition by electrostatic discharge, respectively, the minimum ignition energy of the explosive mixture, afterwards being required an analysis on the possibilities of formation and discharge of electrostatic charge. For the most common combustible dusts, the minimum ignition energy is given, but for new types of flammable substances this parameter defining the sensitivity to ignition of the mixture by electrostatic discharges must be determined. The paper presents the results of research carried out in order to develop the methods and standards for determining the minimum ignition energy of the combustible dust / air mixture and of the methods for the assessment of the risk of ignition of the dust/air explosive atmosphere by electrostatic discharge.
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Karl, T., A. Guenther, A. Turnipseed, P. Artaxo und S. Martin. „Rapid formation of isoprene photo-oxidation products observed in Amazonia“. Atmospheric Chemistry and Physics Discussions 9, Nr. 3 (22.06.2009): 13629–53. http://dx.doi.org/10.5194/acpd-9-13629-2009.
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Abstract. Isoprene represents the single most important reactive hydrocarbon for atmospheric chemistry in the tropical atmosphere. It plays a central role in global and regional atmospheric chemistry and possible climate feedbacks. Photo-oxidation of primary hydrocarbons (e.g. isoprene) leads to the formation of oxygenated VOCs (OVOCs). The evolution of these intermediates affects the oxidative capacity of the atmosphere (by reacting with OH) and can contribute to secondary aerosol formation, a poorly understood process. An accurate and quantitative understanding of VOC oxidation processes is needed for model simulations of regional air quality and global climate. Based on field measurements conducted during the Amazonian aerosol characterization experiment (AMAZE-08) we show that the production of certain OVOCs (e.g. hydroxyacetone) from isoprene photo-oxidation in the lower atmosphere is significantly underpredicted by standard chemistry schemes. A recently suggested novel pathway for isoprene peroxy radicals could explain the observed discrepancy and reconcile the rapid formation of these VOCs. Furthermore, if generalized our observations suggest that prompt photochemical formation of OVOCs and other uncertainties in VOC oxidation schemes could result in substantial underestimates of modelled OH reactivity that could explain a major fraction of the missing OH sink over forests which has previously been attributed to a missing source of primary biogenic VOCs.
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Joutsensaari, J., M. Loivamäki, T. Vuorinen, P. Miettinen, A. M. Nerg, J. K. Holopainen und A. Laaksonen. „Nanoparticle formation by ozonolysis of inducible plant volatiles“. Atmospheric Chemistry and Physics Discussions 5, Nr. 1 (10.01.2005): 1–16. http://dx.doi.org/10.5194/acpd-5-1-2005.
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Abstract. We present the first laboratory experiments of aerosol formation from oxidation of volatile organic species emitted by living plants, a process which for half a century has been known to take place in the atmosphere. We have treated white cabbage crops with methyl jasmonate in order to induce the production of monoterpenes and certain less-volatile sesqui- and homoterpenes. Ozone was introduced into the growth chamber in which the crops were placed, and the subsequent aerosol formation and growth of aerosols were monitored by measuring the particle size distributions continuously during the experiments. Our observations show similar particle formation rates as in the atmosphere but much higher growth rates. The results indicate that the concentrations of nonvolatile oxidation products of plant released precursors needed to induce the nucleation are roughly an order-of-magnitude higher than their concentrations during atmospheric nucleation events. Our results therefore suggest that atmospheric nucleation events proceed via condensation of oxidized organics on pre-existing molecular clusters rather than via their homogeneous or ion-induced nucleation.
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Joutsensaari, J., M. Loivamäki, T. Vuorinen, P. Miettinen, A. M. Nerg, J. K. Holopainen und A. Laaksonen. „Nanoparticle formation by ozonolysis of inducible plant volatiles“. Atmospheric Chemistry and Physics 5, Nr. 6 (16.06.2005): 1489–95. http://dx.doi.org/10.5194/acp-5-1489-2005.
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Abstract. We present the first laboratory experiments of aerosol formation from oxidation of volatile organic species emitted by living plants, a process which for half a century has been known to take place in the atmosphere. We have treated white cabbage plants with methyl jasmonate in order to induce the production of monoterpenes and certain less-volatile sesqui- and homoterpenes. Ozone was introduced into the growth chamber in which the plants were placed, and the subsequent aerosol formation and growth of aerosols were monitored by measuring the particle size distributions continuously during the experiments. Our observations show similar particle formation rates as in the atmosphere but much higher growth rates. The results indicate that the concentrations of nonvolatile oxidation products of plant released precursors needed to induce the nucleation are roughly an order-of-magnitude higher than their concentrations during atmospheric nucleation events. Our results therefore suggest that if oxidized organics are involved in atmospheric nucleation events, their role is to participate in the growth of pre-existing molecular clusters rather than to form such clusters through homogeneous or ion-induced nucleation.
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Thackray, Colin P., und Noelle E. Selin. „Uncertainty and variability in atmospheric formation of PFCAs from fluorotelomer precursors“. Atmospheric Chemistry and Physics 17, Nr. 7 (06.04.2017): 4585–97. http://dx.doi.org/10.5194/acp-17-4585-2017.
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Abstract. Perfluoroalkyl carboxylic acids (PFCAs) are environmental contaminants that are highly persistent, bio-accumulative, and have been detected along with their atmospheric precursors far from emissions sources. The importance of precursor emissions as an indirect source of PFCAs to the environment is uncertain. Modeling studies have used degradation mechanisms of differing complexities to estimate the atmospheric production of PFCAs, and these differing mechanisms lead to quantitatively different yields of PFCAs under differing atmospheric conditions. We evaluate PFCA formation with the most complete degradation mechanism to date, to our knowledge, using a box model analysis to simulate the atmospheric chemical fate of fluorotelomer precursors to long-chain PFCAs. In particular, we examine the variability in PFCA formation in different chemical environments, and estimate the uncertainty in PFCA formation due to reaction rate constants. We calculate long-chain PFCA formation theoretical maximum yields for the degradation of fluorotelomer precursor species at a representative sample of atmospheric conditions from a three-dimensional chemical transport model, and estimate uncertainties in such calculations for urban, ocean, and Arctic conditions using polynomial chaos methods. We find that atmospheric conditions farther from pollution sources have both higher capacities to form long-chain PFCAs and higher uncertainties in those capacities. Our calculations of theoretical maximum yields indicate that under typical Northern Hemisphere conditions, less than 10 % of emitted precursor may reach long-chain PFCA end products. This results in a possible upper bound of 2–50 t year−1 of long-chain PFCA (depending on quantity of emitted precursor) produced in the atmosphere via degradation of fluorotelomer products. However, transport to high-yield areas could result in higher yields. While the atmosphere is a potentially growing source of long-chain PFCAs in the Arctic, oceanic transport and interactions between the atmosphere and ocean may be relatively more important pathways to the Arctic for long-chain PFCAs.
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Полех, Неля, Nelya Polekh, Марина Черниговская, Marina Chernigovskaya, Ольга Яковлева und Olga Yakovleva. „On the formation of the F1 layer during sudden stratospheric warming events“. Solar-Terrestrial Physics 5, Nr. 3 (30.09.2019): 117–27. http://dx.doi.org/10.12737/stp-53201914.
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Using vertical sounding data obtained by the Irkutsk digisonde DPS-4 from 2003 to 2016, we have studied the frequency of occurrence of the F1 layer in winter conditions. The frequency of occurrence of the F1 layer in December–January is shown to be more than twice lower than that in February at any level of magnetic activity. At moderate and low solar activity under quiet geomagnetic conditions, the appearance of F1 layer in midlatitudes of the Northern Hemisphere may be caused by active thermodynamic processes, which lead to transformation or destruction of the circumpolar vortex at heights of the middle atmosphere. Such global dynamic changes occurring in the winter strato-mesosphere are often associated with sudden stratospheric warming events, which are accompanied by increased generation of atmospheric waves of various scales. These wave disturbances can propagate upward to the heights of the lower thermosphere and ionosphere, carrying a significant vertical flow of energy and causing variations in the composition, thermodynamic parameters of the neutral atmosphere and ionosphere.
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Helling, Christiane. „Chemical composition of dust clouds in turbulent brown dwarf atmospheres“. Proceedings of the International Astronomical Union 2, S239 (August 2006): 224–26. http://dx.doi.org/10.1017/s1743921307000476.
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AbstractBrown dwarf atmospheres are largely convective. These convective gas flows collide and feed back a whole spectrum of turbulent fluctuations into the atmospheric fluid field. Resulting non-static density and temperature fields influence the local chemistry concerning gas phase and dust formation. Numerical simulations are used to show the large and inhomogeneous changes of the gas phase chemistry in a turbulent dust forming cloud region of a brown dwarf atmosphere. The relaxation time scale of the gas phase composition towards steady state is considerably longer than for the dust component.
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Shibata, Sho, und Ravit Helled. „Enrichment of Jupiter’s Atmosphere by Late Planetesimal Bombardment“. Astrophysical Journal Letters 926, Nr. 2 (01.02.2022): L37. http://dx.doi.org/10.3847/2041-8213/ac54b1.
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Abstract Jupiter’s atmosphere is enriched with heavy elements by a factor of about 3 compared to a protosolar composition. The origin of this enrichment and whether it represents the bulk composition of the planetary envelope remain unknown. Internal structure models of Jupiter suggest that its envelope is separated from the deep interior and that the planet is not fully mixed. This implies that Jupiter’s atmosphere was enriched with heavy elements just before the end of its formation. Such enrichment can be a result of late planetesimal accretion. However, in situ Jupiter formation models suggest a decreasing accretion rate with increasing planetary mass, which cannot explain Jupiter’s atmospheric enrichment. In this study, we model Jupiter’s formation and show that the migration of proto-Jupiter from ∼20 au to its current location can lead to late planetesimal accretion and atmospheric enrichment. Late planetesimal accretion does not occur if proto-Jupiter migrates only a few astronomical units. We suggest that if Jupiter’s outermost layer is fully mixed and is relatively thin (up to ∼20% of its mass), such late accretion can explain its measured atmospheric composition. It is therefore possible that Jupiter underwent significant orbital migration followed by late planetesimal accretion.
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Schneider, Tapio, und Junjun Liu. „Formation of Jets and Equatorial Superrotation on Jupiter“. Journal of the Atmospheric Sciences 66, Nr. 3 (01.03.2009): 579–601. http://dx.doi.org/10.1175/2008jas2798.1.
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Abstract The zonal flow in Jupiter’s upper troposphere is organized into alternating retrograde and prograde jets, with a prograde (superrotating) jet at the equator. Existing models posit as the driver of the flow either differential radiative heating of the atmosphere or intrinsic heat fluxes emanating from the deep interior; however, they do not reproduce all large-scale features of Jupiter’s jets and thermal structure. Here it is shown that the difficulties in accounting for Jupiter’s jets and thermal structure resolve if the effects of differential radiative heating and intrinsic heat fluxes are considered together, and if upper-tropospheric dynamics are linked to a magnetohydrodynamic (MHD) drag that acts deep in the atmosphere and affects the zonal flow away from but not near the equator. Baroclinic eddies generated by differential radiative heating can account for the off-equatorial jets; meridionally propagating equatorial Rossby waves generated by intrinsic convective heat fluxes can account for the equatorial superrotation. The zonal flow extends deeply into the atmosphere, with its speed changing with depth, away from the equator up to depths at which the MHD drag acts. The theory is supported by simulations with an energetically consistent general circulation model of Jupiter’s outer atmosphere. A simulation that incorporates differential radiative heating and intrinsic heat fluxes reproduces Jupiter’s observed jets and thermal structure and makes testable predictions about as yet unobserved aspects thereof. A control simulation that incorporates only differential radiative heating but not intrinsic heat fluxes produces off-equatorial jets but no equatorial superrotation; another control simulation that incorporates only intrinsic heat fluxes but not differential radiative heating produces equatorial superrotation but no off-equatorial jets. The proposed mechanisms for the formation of jets and equatorial superrotation likely act in the atmospheres of all giant planets.
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Møller, Kristian H., Theo Kurtén, Kelvin H. Bates, Joel A. Thornton und Henrik G. Kjaergaard. „Thermalized Epoxide Formation in the Atmosphere“. Journal of Physical Chemistry A 123, Nr. 49 (12.11.2019): 10620–30. http://dx.doi.org/10.1021/acs.jpca.9b09364.
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Coustenis, Athena. „Formation and Evolution of Titan’s Atmosphere“. Space Science Reviews 116, Nr. 1-2 (Januar 2005): 171–84. http://dx.doi.org/10.1007/s11214-005-1954-2.
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Okita, Toshiichi. „Formation of aerosols in the atmosphere“. Physica Scripta 37, Nr. 2 (01.02.1988): 245–51. http://dx.doi.org/10.1088/0031-8949/37/2/011.
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Cugno, G., P. Patapis, T. Stolker, S. P. Quanz, A. Boehle, H. J. Hoeijmakers, G. D. Marleau, P. Mollière, E. Nasedkin und I. A. G. Snellen. „Molecular mapping of the PDS70 system“. Astronomy & Astrophysics 653 (31.08.2021): A12. http://dx.doi.org/10.1051/0004-6361/202140632.
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Context. Determining the chemical properties of the atmosphere of young forming gas giants might shed light on the location their formation occurred and the mechanisms involved. Aims. Our aim was to detect molecules in the atmosphere of the young forming companion PDS70 b by searching for atmospheric absorption features typical of substellar objects. Methods. We obtained medium-resolution (R ≈ 5075) spectra of the PDS70 planetary system with the SINFONI integral field spectrograph at the Very Large Telescope. We applied molecular mapping, based on cross-correlation with synthetic spectra, to identify signatures of molecular species in the atmosphere of the planet. Results. Although the planet emission is clearly detected when resampling the data to lower resolution, no molecular species could be identified with the cross-correlation technique. We estimated upper limits on the abundances of H2O, CO, and CH4 (log(Xmol) < −4.0, − 4.1, and − 4.9, respectively) assuming a clear atmosphere, and we explored the impact of clouds, which increase the upper limits by a factor of up to 0.7 dex. Assuming that the observations directly probe the planet’s atmosphere, we found a lack of molecular species compared to other directly imaged companions or field objects. Under the assumption that the planet atmosphere presents similar characteristics to other directly imaged planets, we conclude that a dusty environment surrounds the planet, effectively obscuring any feature generated in its atmosphere. We quantify the extinction necessary to impede the detection (AV ≈ 16−17 mag), pointing to the possibility of higher optical thickness than previously estimated from other studies. Finally, the non-detection of molecular species conflicts with atmospheric models previously proposed to describe the forming planet. Conclusions. To reveal how giant planets form a comprehensive approach that includes constraints from multiple techniques needs to be undertaken. Molecular mapping emerges as an alternative to more classical techniques like SED fitting. Specifically tuned atmospheric models are likely required to faithfully describe the atmospheres of forming protoplanets, and higher spectral resolution data may reveal molecular absorption lines despite the dusty environment enshrouding PDS70 b.
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Karl, T., A. Guenther, A. Turnipseed, G. Tyndall, P. Artaxo und S. Martin. „Rapid formation of isoprene photo-oxidation products observed in Amazonia“. Atmospheric Chemistry and Physics 9, Nr. 20 (19.10.2009): 7753–67. http://dx.doi.org/10.5194/acp-9-7753-2009.
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Abstract. Isoprene represents the single most important reactive hydrocarbon for atmospheric chemistry in the tropical atmosphere. It plays a central role in global and regional atmospheric chemistry and possible climate feedbacks. Photo-oxidation of primary hydrocarbons (e.g. isoprene) leads to the formation of oxygenated VOCs (OVOCs). The evolution of these intermediates affects the oxidative capacity of the atmosphere (by reacting with OH) and can contribute to secondary aerosol formation, a poorly understood process. An accurate and quantitative understanding of VOC oxidation processes is needed for model simulations of regional air quality and global climate. Based on field measurements conducted during the Amazonian Aerosol Characterization Experiment (AMAZE-08) we show that the production of certain OVOCs (e.g. hydroxyacetone) from isoprene photo-oxidation in the lower atmosphere is significantly underpredicted by standard chemistry schemes. Recently reported fast secondary production could explain 50% of the observed discrepancy with the remaining part possibly produced via a novel primary production channel, which has been proposed theoretically. The observations of OVOCs are also used to test a recently proposed HOx recycling mechanism via degradation of isoprene peroxy radicals. If generalized our observations suggest that prompt photochemical formation of OVOCs and other uncertainties in VOC oxidation schemes could result in uncertainties of modelled OH reactivity, potentially explaining a fraction of the missing OH sink over forests which has previously been largely attributed to a missing source of primary biogenic VOCs.
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Cridland, Alex J., Ewine F. van Dishoeck, Matthew Alessi und Ralph E. Pudritz. „Connecting planet formation and astrochemistry“. Astronomy & Astrophysics 642 (Oktober 2020): A229. http://dx.doi.org/10.1051/0004-6361/202038767.
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The chemical composition of planetary atmospheres has long been thought to store information regarding where and when a planet accretes its material. Predicting this chemical composition theoretically is a crucial step in linking observational studies to the underlying physics that govern planet formation. As a follow-up to an earlier study of ours on hot Jupiters, we present a population of warm Jupiters (semi-major axis between 0.5 and 4 AU) extracted from the same planetesimal formation population synthesis model as used in that previous work. We compute the astrochemical evolution of the proto-planetary disks included in this population to predict the carbon-to-oxygen (C/O) and nitrogen-to-oxygen (N/O) ratio evolution of the disk gas, ice, and refractory sources, the accretion of which greatly impacts the resulting C/Os and N/Os in the atmosphere of giant planets. We confirm that the main sequence (between accreted solid mass and the atmospheric C/O) we found previously is largely reproduced by the presented population of synthetic warm Jupiters. As a result, the majority of the population falls along the empirically derived mass-metallicity relation when the natal disk has solar or lower metallicity. Planets forming from disks with high metallicity ([Fe/H] > 0.1) results in more scatter in chemical properties, which could explain some of the scatter found in the mass-metallicity relation. Combining predicted C/Os and N/Os shows that Jupiter does not fall among our population of synthetic planets, suggesting that it likely did not form in the inner 5 AU of the Solar System before proceeding into a Grand Tack. This result is consistent with a recent analysis of the chemical composition of Jupiter’s atmosphere, which suggests that it accreted most of its heavy element abundance farther than tens of AU away from the Sun. Finally, we explore the impact of different carbon refractory erosion models, including the location of the carbon erosion front. Shifting the erosion front has a major impact on the resulting C/Os of Jupiter- and Neptune-like planets, but warm Saturns see a smaller shift in C/Os since their carbon and oxygen abundances are equally impacted by gas and refractory accretion.
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Grankin, Dmitry, Irina Mironova, Galina Bazilevskaya, Eugene Rozanov und Tatiana Egorova. „Atmospheric Response to EEP during Geomagnetic Disturbances“. Atmosphere 14, Nr. 2 (30.01.2023): 273. http://dx.doi.org/10.3390/atmos14020273.
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Energetic electron precipitation (EEP) is associated with solar activity and space weather and plays an important role in the Earth’s polar atmosphere. Energetic electrons from the radiation belt precipitate into the atmosphere during geomagnetic disturbances and cause additional ionization rates in the polar middle atmosphere. These induced atmospheric ionization rates lead to the formation of radicals in ion-molecular reactions at the heights of the mesosphere and upper stratosphere with the formation of reactive compounds of odd nitrogen NOy and odd hydrogen HOx groups. These compounds are involved in catalytic reactions that destroy the ozone. In this paper, we present the calculation of atmospheric ionization rates during geomagnetic disturbances using reconstructed spectra of electron precipitation from balloon observations; estimation of ozone destruction during precipitation events using one-dimensional photochemical radiation-convective models, taking into account both parameterization and ion chemistry; as well as provide an estimation of electron density during these periods.
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Keppler, Frank, Mihály Boros, Christian Frankenberg, Jos Lelieveld, Andrew McLeod, Anna Maria Pirttilä, Thomas Röckmann und Jörg-Peter Schnitzler. „Methane formation in aerobic environments“. Environmental Chemistry 6, Nr. 6 (2009): 459. http://dx.doi.org/10.1071/en09137.
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Environmental context. Methane is an important greenhouse gas and its atmospheric concentration has drastically increased since pre-industrial times. Until recently biological methane formation has been associated exclusively with anoxic environments and microbial activity. In this article we discuss several alternative formation pathways of methane in aerobic environments and suggest that non-microbial methane formation may be ubiquitous in terrestrial and marine ecosystems. Abstract. Methane (CH4), the second principal anthropogenic greenhouse gas after CO2, is the most abundant reduced organic compound in the atmosphere and plays a central role in atmospheric chemistry. Therefore a comprehensive understanding of its sources and sinks and the parameters that control emissions is prerequisite to simulate past, present and future atmospheric conditions. Until recently biological CH4 formation has been associated exclusively with anoxic environments and methanogenic activity. However, there is growing and convincing evidence of alternative pathways in the aerobic biosphere including terrestrial plants, soils, marine algae and animals. Identifying and describing these sources is essential to complete our understanding of the biogeochemical cycles that control CH4 in the atmospheric environment and its influence as a greenhouse gas.
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Lampón, M., M. López-Puertas, J. Sanz-Forcada, A. Sánchez-López, K. Molaverdikhani, S. Czesla, A. Quirrenbach et al. „Modelling the He I triplet absorption at 10 830 Å in the atmospheres of HD 189733 b and GJ 3470 b“. Astronomy & Astrophysics 647 (März 2021): A129. http://dx.doi.org/10.1051/0004-6361/202039417.
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Characterising the atmospheres of exoplanets is key to understanding their nature and provides hints about their formation and evolution. High resolution measurements of the helium triplet absorption of highly irradiated planets have been recently reported, which provide a new means of studying their atmospheric escape. In this work we study the escape of the upper atmospheres of HD 189733 b and GJ 3470 b by analysing high resolution He I triplet absorption measurements and using a 1D hydrodynamic spherically symmetric model coupled with a non-local thermodynamic model for the He I triplet state. We also use the H density derived from Lyα observations to further constrain their temperatures, mass-loss rates, and H/He ratios. We have significantly improved our knowledge of the upper atmospheres of these planets. While HD 189733 b has a rather compressed atmosphere and small gas radial velocities, GJ 3470 b, on the other hand with a gravitational potential ten times smaller, exhibits a very extended atmosphere and large radial outflow velocities. Hence, although GJ 3470 b is much less irradiated in the X-ray and extreme ultraviolet radiation, and its upper atmosphere is much cooler, it evaporates at a comparable rate. In particular, we find that the upper atmosphere of HD 189733 b is compact and hot, with a maximum temperature of 12 400−300+400 K, with a very low mean molecular mass (H/He = (99.2/0.8) ± 0.1), which is almost fully ionised above 1.1 RP, and with a mass-loss rate of (1.1 ± 0.1) × 1011 g s−1. In contrast, the upper atmosphere of GJ 3470 b is highly extended and relatively cold, with a maximum temperature of 5100 ± 900 K, also with a very low mean molecular mass (H/He = (98.5/1.5)−1.5+1.0), which is not strongly ionised, and with a mass-loss rate of (1.9 ± 1.1) × 1011 g s−1. Furthermore, our results suggest that upper atmospheres of giant planets undergoing hydrodynamic escape tend to have a very low mean molecular mass (H/He ≳ 97/3).
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Chen, Jiao, Shuai Jiang, Yi-Rong Liu, Teng Huang, Chun-Yu Wang, Shou-Kui Miao, Zhong-Quan Wang, Yang Zhang und Wei Huang. „Interaction of oxalic acid with dimethylamine and its atmospheric implications“. RSC Advances 7, Nr. 11 (2017): 6374–88. http://dx.doi.org/10.1039/c6ra27945g.
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Moldenhauer, T. W., R. Kuiper, W. Kley und C. W. Ormel. „Steady state by recycling prevents premature collapse of protoplanetary atmospheres“. Astronomy & Astrophysics 646 (Februar 2021): L11. http://dx.doi.org/10.1051/0004-6361/202040220.
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Context. In recent years, space missions such as Kepler and TESS have discovered many close-in planets with significant atmospheres consisting of hydrogen and helium: mini-Neptunes. This indicates that these planets formed early in gas-rich disks while avoiding the runaway gas accretion that would otherwise have turned them into hot-Jupiters. A solution is to invoke a long Kelvin-Helmholtz contraction (or cooling) timescale, but it has also been suggested that thermodynamical cooling can be prevented by hydrodynamical planet atmosphere-disk recycling. Aims. We investigate the efficacy of the recycling hypothesis in preventing the collapse of the atmosphere, check for the existence of a steady state configuration, and determine the final atmospheric mass to core mass ratio. Methods. We use three-dimensional radiation-hydrodynamic simulations to model the formation of planetary proto-atmospheres. Equations are solved in a local frame centered on the planet. Results. Ignoring small oscillations that average to zero over time, the simulations converge to a steady state where the velocity field of the gas becomes constant in time. In a steady state, the energy loss by radiative cooling is fully compensated by the recycling of the low entropy gas in the planetary atmosphere with high entropy gas from the circumstellar disk. Conclusions. For close-in planets, recycling naturally halts the cooling of planetary proto-atmospheres, preventing them from contracting toward the runaway regime and collapsing into gas giants.
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Kang, Zhiqin, Zhijing Wang, Yang Lu, Ran Cao, Dongwei Huang und Qiaorong Meng. „Investigation on the Effect of Atmosphere on the Pyrolysis Behavior and Oil Quality of Jimusar Oil Shale“. Geofluids 2022 (02.03.2022): 1–9. http://dx.doi.org/10.1155/2022/1408690.
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High-temperature H2O and CO2 can improve the pyrolysis behavior of oil shale. Therefore, in this paper, Jimusar oil shale was selected as the research object and the effect of the reaction atmosphere (H2O, CO2, and N2) on its pyrolysis behavior, pyrolysate distribution, and pyrolysis oil quality was fully compared and studied. The results showed that compared with the N2 atmosphere, the presence of H2O and CO2 both increased the weight loss and weight loss rate during pyrolysis of oil shale and the existence of H2O advanced the initial precipitation temperature of volatiles by 17°C. The comprehensive release characteristic indices of volatiles during pyrolysis of oil shale in the CO2 and H2O atmospheres increased by 49.34% and 114.35%, respectively, which significantly improved its pyrolysis reactivity. Both H2O and CO2 atmospheres improved the pyrolysis oil yield of oil shale, and the pyrolysis oil yield in the H2O atmosphere performed better than that in the CO2 atmosphere. Especially, the H2O atmosphere could increase the pyrolysis oil yield by 41.42%. The existence of CO2 prevented methyl radicals from accepting hydrogen radicals during pyrolysis and reduced the alkane yield, while CO2 participated in the addition reaction of alkane, which increased the alkene yield. High-temperature H2O provided more hydrogen source, which increased the alkane yield and inhibited the alkene formation. Both H2O and CO2 atmospheres promoted the cracking of polycyclic aromatics and increased the yield of small-molecular aromatics in the pyrolysis oil. During the pyrolysis process of oil shale, CO2 and H2O underwent reforming reaction with the heavy oil, which increased the light component fraction, thereby increasing the H/C ratio of pyrolysis oil. Thus, the existence of H2O and CO2 atmospheres improved the quality of pyrolysis oil and the effect of H2O was better than CO2. The H2O and CO2 atmosphere promoted the formation of a well-developed pore structure, which was conducive to mass and heat transfer during pyrolysis of oil shale.
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Kotobuki, Masashi, Binngong Yan, Li Lu, Emil Hanc und Joanna Molenda. „Study on stabilization of cubic Li7La3Zr2O12 by Ge substitution in various atmospheres“. Functional Materials Letters 09, Nr. 06 (Dezember 2016): 1642005. http://dx.doi.org/10.1142/s1793604716420054.
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Stabilization of high Li ion conductive cubic Li7La3Zr2O[Formula: see text] (LLZ) by Ge substitution in air, N2/O2 and N2 atmospheres are studied by high temperature XRD (HT-XRD) of Ge-added tetragonal LLZ (Ge-LLZ). A formation of low temperature cubic phase caused by CO2 absorption during storage of the Ge-LLZ is observed at about 160[Formula: see text]C in all atmospheres. Additionally, impurity formation of La2Zr2O7 and La2O3 also occurs in all atmospheres. On the other hand, stabilization of cubic phase by substitution of Ge is largely influenced by the atmosphere. The cubic phase is observed at 40[Formula: see text]C after heating Ge-LLZ to 700[Formula: see text]C in air while only tetragonal phase appeared after heating in N2/O2. It is concluded that the heating atmosphere largely influences substitution of Ge, resulting in stabilization of the high Li ion conductive cubic phase.
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Zanca, Tommaso, Jakub Kubečka, Evgeni Zapadinsky, Monica Passananti, Theo Kurtén und Hanna Vehkamäki. „Highly oxygenated organic molecule cluster decomposition in atmospheric pressure interface time-of-flight mass spectrometers“. Atmospheric Measurement Techniques 13, Nr. 7 (03.07.2020): 3581–93. http://dx.doi.org/10.5194/amt-13-3581-2020.
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Abstract. Identification of atmospheric molecular clusters and measurement of their concentrations by atmospheric pressure interface time-of-flight (APi-TOF) mass spectrometers may be affected by systematic error due to possible decomposition of clusters inside the instrument. Here, we perform numerical simulations of decomposition in an APi-TOF mass spectrometers and formation in the atmosphere of a set of clusters which involve a representative kind of highly oxygenated organic molecule (HOM), with the molecular formula C10H16O8. This elemental composition corresponds to one of the most common mass peaks observed in experiments on ozone-initiated autoxidation of α-pinene. Our results show that decomposition is highly unlikely for the considered clusters, provided their bonding energy is large enough to allow formation in the atmosphere in the first place.