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1.
Flavio Scappini Cesare Cecchi-Pestellini Harvey Smith William Klemperer Alexander Dalgarno 《Monthly notices of the Royal Astronomical Society》2003,341(2):657-661
We consider sulphur depletion in dense molecular clouds, and suggest hydrated sulphuric acid, H2 SO4 · n H2 O, as a component of interstellar dust in icy mantles. We discuss the formation of hydrated sulphuric acid in collapsing clouds and its instability in heated regions in terms of the existing hot core models and observations. We also show that some features of the infrared spectrum of hydrated sulphuric acid have correspondence in the observed spectra of young stellar objects. 相似文献
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The processes by which energetic electrons lose energy in a weakly ionized gas of argon are analysed and calculations are carried out taking into account the discrete nature of the excitation processes. The excitation, ionization and heating efficiences are computed for energies up to 200 eV absorbed in a gas with fractional ionizations varying up to 10?2. 相似文献
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西藏羊八井热田地热流体成因及演化的惰性气体制约 总被引：4，自引：5，他引：4
地热流体中惰性气体的相对丰度和同位素组成，不仅可以揭露热田的热源性质，而且还能够揭示深，浅层地热流体的内在联系和演化过程等。在西藏羊八井热田的地热气体中，已检测出大量的^4He组分，3He/^4He值是大气的0．087－0．259倍，表明深部地壳物质的局部熔融为热田提供能量，浅层地热流体的3He/4He 值自西北向东南呈降低趋势，与热储温度的变化相一致，反映出侧向运移时补充了更多的壳源氦，热田北区深层地热流体具有稍高的3He/4He值，是浅层地热流体的母源，气体中氪和氙的相对丰度具有大气降水成因的特征，结合现有的实际资料，建立了热田地热流体的概念模型。 相似文献
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Observations of molecules and dust in supernova SN 1987a and SN 1995ad are summarised and the inferred masses of CO and SiO
are presented. The chemistry is used to argue that macroscopic mixing occurred in which the interpenetrating clumps in the
ejecta retained their microscopic integrity. An explanation of the anomalous temperature structure is advanced. Molecular
candidates for some of the unidentified spectral features are proposed.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
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The SE Pacific stock of Patagonian grenadier (Macruronus magellanicus) showed evidence of an abrupt reduction in recruitment after 2000. This drop exceeded expectations from changes in the spawning stock biomass (SSB), indicating a change in the stock-recruitment relationship (S-R). We evaluated whether variability in recruitment could be explained by concurrent changes in three environmental indices: sea-surface temperature anomaly (SSTA); southern oscillation index (SOI); and latitudinal position of the west wind drift bifurcation (WWDL). Continuous and discrete effects of these indices were tested as covariates in linear log-log and non-linear Ricker's S-R models. Discrete effects represented regime shifts detected in SSTA (1998), SOI (1998) and WWDL (1995). While SSTA was the only continuous variable found to be significant, the discrete 1998 regime shift supported the most informative model. The best Ricker's model considered a discrete intercept change in the same year: 1998. Although a spurious correlation between SSTA and S-R changes is possible, SSTA may be reflecting major physical or biological changes relevant to M. magellanicus juveniles in the SE Pacific. 相似文献
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We investigate the response of an atmosphere of argon to solar ultra-violet radiation. With the assumption that Mercury has an argon atmosphere that is optically thick to ionizing radiation the intensities of the ultra-violet dayglow lines resulting from photoelectron impact are calculated. For most of the model atmospheres, the predicted intensities are above the detection threshold of the 1973 Venus-Mercury ultra-violet spectrometer of Broadfoot, McElroy and Belton. 相似文献
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V.A. KrasnopolskyD.J. Christian V. KharchenkoA. Dalgarno S.J. WolkC.M. Lisse S.A. Stern 《Icarus》2002,160(2):437-447
Comet McNaught-Hartley was observed in five 1-h exposures on January 8-14 2001 using the advanced CCD imaging spectrometer on board the Chandra X-ray Observatory. The X-ray image of the comet does not show a crescent-like shape. The brightest region is offset from the nucleus between the sunward and comet velocity directions. The comet mean X-ray luminosity is equal to 7.8×1015 erg s−1 for photon energy E>150 eV and aperture ρ=1.5×105 km where the comet X-ray brightness exceeds 20% of the peak value. Gas production rate was 1029 s−1 during the observations, and the efficiency of X-ray excitation was equal to 4×10−14 erg AU3/2. Day-to-day variations in X-rays reached a factor of 5. The strongest short-term variation was by a factor of 1.75 for 1600 s. This variation may be explained by a decline in the solar-wind flux by the same factor in ≈800 s. The comet and Earth were seeing different faces of the Sun, and time delay in the solar-wind events on the Earth and the comet was long, equal to 6 days. The best correlation between the comet X-ray luminosity and the solar-wind proton density is for the time delay of 5.5 days and may be explained by the higher velocity of heavy ions.Careful background subtraction made it possible to extract the comet spectrum from 150 to 1000 eV. No signal was detected at E>1000 eV, and a 3σ upper limit to any emission with E>1000 eV is 0.3% of the photon emission at 150-1000 eV. The best χ2-fit model to the spectrum consists of nine narrow emission features. The emission energies and intensities are in good agreement with a charge exchange spectrum calculated by us for the slow solar wind. Using this spectrum, we identify the observed emissions as (Ne7++Mg7++Mg8+) at 195 eV, (Mg8++Mg9++Si8+) at 250 eV, C5+ at 370 and 460 eV, O6+ at 560 eV, O7+ at 650, 780, and 840 eV, and Ne8+ at 940 eV. X-ray spectroscopy of comets may be used to diagnose the solar-wind composition and its interaction with comets. 相似文献