共查询到20条相似文献，搜索用时 109 毫秒
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In crossed-beam experiments, reactive cross-sections for the oxidation of groundstate Ba and Sr atoms by oxygen molecules were determined over a wide range of relative collisional energies (0.1–1 eV). On the basis of rate constants, thus derived, it is shown that Ba oxidation in upper atmosphere releases proceeds predominantly via optically pumped metastable Ba states, whereas SrO concentrations will be too low to be seen, because an equilibrium unfavorable to oxide formation is established. 相似文献
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During the last two decades the theory of degenerate stellar configurations has been developed in works by Ambartsumian and Sahakian, as well as in some other papers. This article is further progress in this direction. Systematic investigations of thermodynamic properties of the ground and metastable states of degenerate plasma have been carried out over the total range of pressures. It was found that in the range of densities 3×1010???3×1014 g cm?3 there exists a pionization effect which plays an important role in the thermodynamics of degenerate plasma. The pion condensate present in nuclear matter promotes the existence of metastable nuclear clusters with the nuclear numberA?106. The equation of state of degenerate stellar matter has been notably revised and, accordingly, the neutron star parameters have been calculated anew. The role of the pion condensate in generating strong magnetic fields observed in the pulsars is discussed. 相似文献
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Abstract— The hypothesis that the soluble fraction of the organic compounds present in carbonaceous chondrite meteorites was formed during aqueous alteration of the parent body was tested with mass‐transfer, reaction‐path calculations. In these calculations, we start with likely compositions of the original parent body and asteroidal fluids that are far from thermodynamic equilibrium, and metastable and stable equilibrium constraints are imposed as the total Gibbs free energy of the parent body environment is minimized. The results of these calculations suggest that the classes of soluble organic compounds present in carbonaceous chondrite meteorites could have formed during relatively low temperature aqueous alteration of the meteorite parent body or bodies. The main controls on the potential for synthesis and transformation of organic compounds were the oxidation state of the rock/fluid system, the bulk composition of that system, and the temperatures that were achieved during the alteration event or events. It also appears that the alteration mineral assemblages were influenced by the presence of soluble organic compounds and reaction among them. 相似文献
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In this paper, we suggest that a solar flare may be triggered by a lack of thermal equilibrium rather than by a magnetic instability. The possibility of such a thermal nonequilibrium (or catastrophe) is demonstrated by solving approximately the energy equation for a loop under a balance between thermal conduction, optically thin radiation and a heating source. It is found that, if one starts with a cool equilibrium at a few times 104 K and gradually increases the heating or decreases the loop pressure (or decreases the loop length), then, ultimately, critical metastable conditions are reached beyond which no cool equilibrium exists. The plasma heats up explosively to a new quasi-equilibrium at typically 107 K. During such a thermal flaring, any magnetic disruption or particle acceleration are secondary in nature. For a simple-loop (or compact) flare, the cool core of an active-region loop heats up and the magnetic tube of plasma maintains its position. For a two-ribbon flare, the material of an active-region (or plage) filament heats up and expands along the filament; it slowly rises until, at a critical height, the magnetic configuration becomes magnetohydrodynamically unstable and erupts violently outwards. In this case thermal nonequilibrium acts as a trigger for the magnetic eruption and subsequent magnetic energy release as the field closes back down. 相似文献
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The expected proton and neutrino fluxes from decays of massive metastable relic particles are calculated using the HERWIG QCD event generator. The predicted proton spectrum can account for the observed flux of extremely high energy cosmic rays beyond the Greisen-Zatsepin-Kuzmin cutoff, for a decaying particle mass of
(1012) GeV. The lifetime required is of
(1020) yr if such particles constitute all of the dark matter (with a proportionally shorter lifetime for a smaller contribution). Such values are plausible if the metastable particles are hadron-like bound states from the hidden sector of supersymmetry breaking which decay through nonrenormalizable interactions. The expected ratio of the proton to neutrino flux is given as a diagonistic of the decaying particle model for the forthcoming Pierre Auger Project. 相似文献
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Jérôme Gattacceca Roger H. Hewins Jean‐Pierre Lorand Pierre Rochette France Lagroix Cécile Cournède Minoru Uehara Sylvain Pont Violaine Sautter Rosa. B. Scorzelli Chrystel Hombourger Pablo Munayco Brigitte Zanda Hasnaa Chennaoui Ludovic Ferrière 《Meteoritics & planetary science》2013,48(10):1919-1936
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Frans J. M. Rietmeijer Aurora Pun Joseph A. Nuth III 《Monthly notices of the Royal Astronomical Society》2009,396(1):402-408
Here, we report on a kinetically controlled vapour phase condensation experiment using a low-calcium Ca–Fe–SiO–H2 –O2 vapour. Under these conditions of extreme disequilibrium, the condensate properties become predictable. They are amorphous solids with (predictable) deep metastable eutectic compositions. This study also shows how chemical evolution of the condensate grains will lead to chemically complex amorphous solids. The highly disordered structure of the deep metastable eutectic condensates is the very key to this predictable chemical evolution to grains with a silicate mineral composition, yet being amorphous. We compare our results with astronomical observations of dust around young stellar objects. 相似文献
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Arthur B. C. Walker Jr. 《Solar physics》1988,118(1-2):209-229
Non-thermal phenomena on the Sun are characterized by the transient acceleration of electrons and ions to energies ranging from several keV to tens of GeV, and the impulsive heating of plasma to temperatures exceeding 5 × 107 K. These energetic processes result in the emission of a broad spectrum of electromagnetic radiation and of high-energy neutrons, as well as the escape of high energy electrons and ions from the acceleration region. The determination of the energy spectrum, polarization, and spatial distribution of these emissions, which contain detailed information on the acceleration and heating process, and the conditions at the sites at which this energy is generated and dissipated, is the principal objective of high-energy solar studies.The study of the evolution of magnetic structures in the solar convection zone and atmosphere which underlie the metastable conditions which precede these energetic processes, of the conditions that trigger the release of energy, and of the impact of the energy released on the solar atmosphere, is most effectively carried out by observations of thermal and quasi-thermal phenomena which precede, coincide with, and follow the impulsive acceleration and heating event itself. Multispectral observations of the phenomena associated with non-thermal events on the Sun are reviewed, and the requirements for visible, ultraviolet, extreme ultraviolet, and soft X-ray observations which are necessary for future advances are briefly described. 相似文献
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J.L. Carlsten 《Planetary and Space Science》1975,23(1):53-60
The photoionization of optically thin barium clouds is analyzed and shown to occur primarily by a two-step process involving the metastable term as the ntermediate state. The equilibrium populations of the and metastable levels are calculated and found to differ significantly from the values now in the literature. These populations are combined with our newly available photoionization data to calculate the resulting photoionization rate in the upper atmosphere. 相似文献
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Three small samples of the Odessa, Texas iron meteorite, two surrounded by sandy soil, were introduced into a hydrogen plasma. The soil was effectively cleansed from the iron surfaces, being substantially destroyed with only a fine dust remaining. The appearance of the iron meteorite samples indicated that the terrestrial oxidation was reversed, probably to magnetite, Fe3O4, and metallic iron. 相似文献
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The first order deconfinement phase transitions in rotating hybrid stars are studied and it is found that if the surface tension is sufficiently large, the transition from metastable hadron matter to stable mixed hadron-quark matter during the spindown history of a hybrid star can cause a glitch. 相似文献
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A. MORLOK Y. C. SUTTON N. St. J. BRAITHWAITE Monica M. GRADY 《Meteoritics & planetary science》2012,47(12):2269-2280
We are investigating chondrule formation by nebular shock waves, using hot plasma as an analog of the heated gas produced by a shock wave as it passes through the protoplanetary environment. Precursor material (mainly silicates, plus metal, and sulfide) was dropped through the plasma in a basic experimental set‐up designed to simulate gas–grain collisions in an unconstrained spatial environment (i.e., no interaction with furnace walls during formation). These experiments were undertaken in air (at atmospheric pressure), to act as a “proof‐of‐principle”—could chondrules, or chondrule‐analog objects (CAO), be formed by gas–grain interaction initiated by shock fronts? Our results showed that if accelerating material through a fixed plasma field is a valid simulation of a supersonic shock wave traveling through a cloud of gas and dust, then CAO certainly could be formed by this process. Melting of and mixing between starting materials occurred, indicating temperatures of at least 1266 °C (the olivine‐feldspar eutectic). The production of CAO with mixed mineralogy from monomineralic starting materials also shows that collisions between particles are an important mechanism within the chondrule formation process, such that dust aggregates are not necessarily required as chondrule precursors. Not surprisingly, there were significant differences between the synthetic CAO and natural chondrules, presumably mainly because of the oxidizing conditions of the experiment. Results also show similarity to features of micrometeorites like cosmic spherules, particularly the dendritic pattern of iron oxide crystallites produced on micrometeorites by oxidation during atmospheric entry and the formation of vesicles by evaporation of sulfides. 相似文献
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Frans J. M. RIETMEIJER 《Meteoritics & planetary science》2004,39(11):1869-1887
Abstract— Petrological changes in Ni‐free and low‐Ni pyrrhotite, and much less in pentlandite, during atmospheric entry flash‐heating of the sulfide IDPs L2005E40, L2005C39, and L2006A28 support 1) ferrous sulfide oxidation with vacancy formation and Fe3+ ordering; and 2) Fe‐oxide formation and sulfur vapor loss through abundant vesicles. Melting of metastable chondritic aggregate materials at the IDP surface has occurred. All changes, e.g., formation of a continuous maghémite rim, proceeded as solid‐state reactions at a peak heating temperature of ?700 °C. This temperature in combination with particle size and density suggest a ?10 km/s?1 entry velocity. The IDPs probably belonged to cluster IDPs that entered the atmosphere with near‐Earth or Earth‐crossing asteroid velocities. They could be debris from extinct or dormant comet nuclei, which is consistent with shock comminution of pyrrhotite in these IDPs. 相似文献
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G. A. Gurzadyan 《Astrophysics and Space Science》1981,80(1):189-195
The possiblity of the excitation of a new class of spectral lines, so calledpseudo-resonance absorption lines in the conditions of planetary nebulae, is predicted. These lines are formed by permitted atomic transitions from the metastable levels to the upper subordinate, but not metastable, levels. To observe pseudo-resonance lines of nebular origin is possible only on the spectra of the nuclei of planetary and diffuse nebulae in the form of absorption lines.The preliminary list of pseudo-resonance lines is given in Table I; all of them are located in the region of vacuum ultra-violet (1000–3000 Å), therefore, their observation is possible only under space conditions.In stellar photospheres as well as in the interstellar medium the formation of pseudo-resonance lines is impossible. 相似文献
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Auroral ultraviolet spectra in the range 1200–3200 A have been obtained by the spectrometer onboard the OGO-4 satellite. Emissions of N2, H, O and N are readily identified. Atomic and molecular intensities are deduced from the comparison with a synthetic spectrum and compare reasonably well with some previous measurements and calculations. A feature at 2150 A is assigned to the (1-0) NO γ band. Taking into consideration the various excitation mechanisms of NO(A2σ) we propose that the energy transfer from N2 metastable molecules to oxygen accounts for the excitation of the NO γ bands. In particular, we suggest that the resonant reaction between O2 and highly metastable N2(W3Δ) molecules may be a major source of NO(A2σ). 相似文献
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Pedro Patiño 《Astrophysics and Space Science》1997,256(1-2):523-527
The oxidation of four alkanes, two olefins and twelve aromatic compounds in the liquid phase with either high voltage or radio frequency glow discharges has been studied. The results of the liquid-plasma interactions of this work considerably differ from those in homogeneous gas phase. Neither fragmentation products in the traps nor polymers on the reactor walls have been detected. The selectivity of product formation is far superior to plasma oxidations in gas phase, making these techniques attractive for preparative chemistry. Total conversion, i.e., mass transformed against initial mass of substrate, has been studied as a function of the temperature of the liquid and the oxygen flow rate in the reactor. Optical emission spectroscopy has been utilized to detect and monitor the active species in the plasma. At the conditions for maximum oxidation no evidence of O2(1g) has been observed. A correlation between the behavior of the O(3P) population in the discharge and the reactivity of the different compounds, as a function of the oxygen flow rate in the reactor, is presented. 相似文献
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Frans J. M. Rietmeijer 《Meteoritics & planetary science》1993,28(2):242-245
Abstract I present an internally consistent reinterpretation of carbyne diffraction data making a few plausible assumptions. The results support that carbynes could be crystalline, randomly interstratified (or mixed-layered) carbons with variable C/(C+H+O+N) ratios rather than thermodynamically stable carbon allotropes. The metastable carbynes are likely the result of incomplete, kinetically-inhibited, low-temperature pyrolysis of precursor material. A renewed interest in meteoritic carbynes should seek to combine light-element chemistry and crystallography of these elusive carbons. 相似文献
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E.C. Zipf 《Planetary and Space Science》1985,33(11):1303-1307
The single and double ionization of atomic oxygen by electron impact has been studied, and the energy dependence of the specific ionization cross-section, σ(O+) and σ(O2+), has been measured from 40 to 300 eV using a high-density atomic oxygen source not contaminated by metastable O(1D) or O(1S) atoms. 相似文献