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1.
This paper has been devoted to a basic molecular studies of polyatomics. A critical analysis of the 70 available references in literature has been made to select 37 polyatomic molecules, molecular ions, and radicals containing six, seven, eight, nine, ten, eleven, twelve, and thirteen atoms of astrophysical significance. The results have been arranged in a text-cum-tabular form. The compilation contains various information for each molecule, such as the spectral region, transition levels, astrophysical objects where the respective molecules have been detected (say, comet, meteorite, Sun, planet, star, interstellar matter, interstellar cloud, molecular cloud, interstellar space, Galaxy, etc.). Two-hundred fourteen new polyatomic molecules (containing 6, 7, 8, 9, and 10 atoms) of astrophysical significance have also been listed.Astrophysics and Space Science Review Paper II. 相似文献
2.
One hundred and fifty-three diatomic molecules,molecular ions,and radicals of astrophysical interest
A critical analysis of the 583 available references in literature has been made to select 153 diatomic molecules, molecular ions, and radicals of astrophysical significance. The results have been arranged in a text-cum-tabular form. The compilation contains various information for each molecule, such as the dissociation energy, spectral region, transition levels, astrophysical objects where the respective molecules have been detected (say, comet, meteorite, Sun, planet, star, interstellar matter, Galaxy, etc.); computed theoretical parameters (i.e., FCFs, transition probabilities, r-centroids, PE curves), and available laboratory data with respective references.In many problems involving the estimation of the physical condition (viz., temperature, pressure, density, and abundance) of the emitter, in various cosmic sources, it is desirous to have a knowledge of the theoretical parameters as well as the experimental details for the molecular spectra of interest.A few important areas of active research in laboratory astrophysics have also been identified in this article: laboratory astrophysics, molecular cloud chemistry, isotopic abundance, planetary and cometary atmospheres through satellites.Besides, some interesting plots of the dissociation energy vs molecular weight, dissociation energy vs total atomic number, dissociation energy vs atomic number differences, ionization potential vs total atomic number, ionization potential vs atomic number differences, and ionization potential vs molecular weight for respective molecules have also been enumerated. Thirty-one new diatomic molecules/molecular ions/radicals of astrophysical significance have also been listed.Astrophysics and Space Science Review Paper. 相似文献
3.
Summary The presence of solid carbon monoxide (CO) on interstellar grains was confirmed observationally in 1984 with the detection of infrared absorption at 4.67m wavelength in several molecular clouds. Subsequent observations suggest that solid CO is ubiquitous in the quiescent molecular cloud environment. In some lines of sight, the degree of frosting on to grains is sufficient to reduce appreciably the abundance of CO remaining in the gas, a result of considerable astrophysical significance: in addition to its importance as a tracer of molecular material, CO is vital to the production of many polyatomic molecules by gas phase reaction schemes, and its depletion could have a dramatic effect on the abundances of more complex carbon-bearing molecules. The infrared spectrum of solid CO provides an important diagnostic of the chemical composition and thermal evolution of grain mantles, leading to the prediction that CO2 is also present in solid form.As it is now some six years since observations of interstellar solid CO were first reported, this is an appropriate time to review the topic and to suggest some directions for future research. The introduction (Sect. 1) attempts to place the subject in its broader astrophysical context. The infrared observations and their implications are discussed in detail in Sect. 2. The question of the degree of CO depletion implied by the observations of both solid state and gas phase CO is re-examined in Sect. 3. We assess the possibility of CO detection by means of solid state absorption or luminescence in the ultraviolet in Sect. 4. Future prospects are summarised in the final section.This article was processed by the author using the Springer-Verlag TEX Theaar macro package 1988. 相似文献
4.
The results of astrophysical observations that provide evidence for the molecular origin of the diffuse interstellar bands (DIBs) are reviewed. It is established that molecular systems with a linear, planar or spherical carbon skeleton are good candidates as DIB carriers, and laboratory spectroscopic data concerning such systems are discussed. The characteristic features of the electronic spectra of fullerenes, polycyclic aromatic hydrocarbons, and of linear carbon chains and their ions are found to be consistent with the principal spectroscopic features of DIBs. Analysis of the astrophysical electronic spectra of several simple molecules that have so far been assigned indicates that polar molecules should be easier to detect in this way than those without a permanent electric dipole moment. 相似文献
5.
We have calculated the opacity as resulting from different interstellar grain models, molecules, atoms, and ions. The resulting opacities have been applied to a numerical code used to follow the thermal evolution of a contracting cloud in one dimension. An exact analytical and computational developments of both Mie theory for isolated grains and Güttler's formulae for composite grain models have been used to calculate the extinction coefficients. We have studied two models of composite grain and three models of isolated grain. The opacity of interstellar grains has been calculated in the temperature range 10–1500 K. The molecular opacity is splitted into continuous and line opacities. The different sources of continuous opacity have been studied. The line opacity has also been included. The atomic opacities are also considered. The hydrodynamical equations are solved explicitly but the energy and Poisson equations are solved implicitly.It has been found that the thermal evolution during contraction of protostellar clouds is sensitive to both: the assumed grain models and the considered chemical composition. A cloud of an initial temperature of 10 K collapsed to a stage in which the temperature increases to 91 000 K and the density reached to 0.16 g cm–3. 相似文献
6.
Selected examples of the use of observationally inferred molecular level populations and chemical compositions in the diagnosis
of interstellar sources and processes important in them (and in other diffuse astrophysical sources) are given. The sources
considered include the interclump medium of a giant molecular cloud, dark cores which are the progenitors of star formation,
material responding to recent star formation and which may form further stars, and stellar ejecta (including those of supernovae)
about to merge with the interstellar medium. The measurement of the microwave background, mixing of material between different
nuclear burning zones in evolved stars and turbulent boundary layers (which are present in and influence the structures and
evolution of all diffuse astrophysical sources) are treated. 相似文献
7.
The Sun may well have formed in the type of interstellar cloud currently referred to as a cold, dark cloud. We present current tabulations of the totality of known interstellar molecules and of the subset which have been identified in cold clouds. Molecular abundances are given for two such clouds which show interesting chemical differences in spite of strong physical similarities, Taurus Molecular Cloud 1 (TMC-1) and Lynd's 134N (L134N, also referred to as L183). These regions may be at different evolutionary stages. 相似文献
8.
A theoretical treatment is given of the growth of grains as a consequence of their mutual coagulation brought about by relative motions induced by radiation pressure. Analytical and numerical techniques are employed to tackle the relevant coagulation equation. The results are of particular astrophysical significance in the context of forming very small grains following a nucleation process, in the production of grains large enough to allow condensation of volatiles onto their surface, and in any situation where the supply of volatiles has been exhausted. It was found that in interstellar clouds, grains composed of iron, graphite and glassy carbon, being typical examples of three basic types of material, could grow to a size where condensation of the volatiles was possible. On the other hand, olivine, a typical silicate, could not. If a source of radiation existed at the centre of the cloud, then growth could occur if the cloud was turbulent or if the density was high enough; otherwise the grains were driven out of the regions of interest at high velocity. In the latter case, with a high cloud density, re-radiation has to be taken into account. 相似文献
9.
Broten NW MacLeod JM Avery LW Irvine WM Hoglund B Friberg P Hjalmarson A 《The Astrophysical journal》1984,(1):L25-L29
A new interstellar molecule, methylcyanoacetylene (CH3C3N), has been detected in the molecular cloud TMC-1. The J = 8 --> 7, J = 7 --> 6, J = 6 --> 5, and J = 5 --> 4 transitions have been observed. For the first three of these, both the K = 0 and K = 1 components are present, while for J = 5 --> 4, only the K = 0 line has been detected. The observed frequencies were calculated by assuming a value of radial velocity VLSR = 5.8 km s-1 for TMC-1, typical of other molecules in the cloud. All observed frequencies are within 10 kHz of the calculated frequencies, which are based on the 1982 laboratory constants of Moises et al., so the identification is secure. The lines are broadened by hyperfine splitting, and the J = 5 --> 4, K = 0 transition shows incipient resolution into three hyperfine components. The rotational temperature determined for these observations is quite low, with 2.7 K < or = Trot < or = 4 K. the total column density is approximately 5 x 10(12) cm-2. 相似文献
10.
Helen J. Fraser † Mark P. Collings Martin R. S. McCoustra David A. Williams 《Monthly notices of the Royal Astronomical Society》2001,327(4):1165-1172
Water (H2 O) ice is an important solid constituent of many astrophysical environments. To comprehend the role of such ices in the chemistry and evolution of dense molecular clouds and comets, it is necessary to understand the freeze-out, potential surface reactivity and desorption mechanisms of such molecular systems. Consequently, there is a real need from within the astronomical modelling community for accurate empirical molecular data pertaining to these processes. Here we give the first results of a laboratory programme to provide such data. Measurements of the thermal desorption of H2 O ice, under interstellar conditions, are presented. For ice deposited under conditions that realistically mimic those in a dense molecular cloud, the thermal desorption of thin films (≪50 molecular layers) is found to occur with zeroth-order kinetics characterized by a surface binding energy, E des , of 5773 ± 60 K, and a pre-exponential factor, A , of 1030 ± 2 molecules cm−2 s−1 . These results imply that, in the dense interstellar medium, thermal desorption of H2 O ice will occur at significantly higher temperatures than has previously been assumed. 相似文献
11.
Markandey Singh 《Astrophysics and Space Science》1988,140(2):421-427
The dissociation energy and ionization potential of 97 diatomic molecules, molecular ions, and radicals according to their molecular weight have been listed in tabular form.Some interesting plots of the dissociation energy vs molecular weight, dissociation energy vs total atomic number, and dissociation energy vs atomic number differences for respective molecules have also been enumerated.Thirty one new diatomic molecules/molecular ions/radicals of astrophysical significance have also been listed on the basis of theoretical grounds. 相似文献
12.
Laboratory and theoretical studies have been made of the effects of ultraviolet photolysis of interstellar grain mantles which consist of combinations of hydrogen, oxygen, carbon and nitrogen — dirty ice. It is shown that processes involving photolysis (photoprocessing) of interstellar grains are important during most of their lifetime even including the time they spend in dense clouds. A laboratory designed to simulate the interstellar conditions is described. This is the first time such a laboratory has been able to provide results which may be directly scaled to the astrophysical situations involving interstellar grains and their environment. The evolution of grain analogs is followed by observing the infrared absorption spectra of photolyzed samples of ices deposited at 10 K. The creation and storage of radicals and the production of molecules occur as a result of reactions within the solid. A large number of molecules and radicals observed in the interstellar gas appear in the irradiated ices. Energy released during warm-up is seen from visible luminescence and inferred from vapor pressure enhancement which occurs during warming of photolyzed samples relative to unphotolyzed samples. The evolution of a grain and its role as a source as well as a sink of molecules is pictured as a statistical process within dense clouds. The gradual accretion on and photolysis of an individual grain provides the stored chemical energy the release of which is sporadically triggered by relatively mild events (such as low velocity grain-grain collisions) to produce the impulsive heating needed to eject or evaporate a portion of the grain mantle. An extremely complex and rather refractory substance possessing the infrared signatures of amino groups and carboxylic acid groups and having a maximum mass of 514 amu has been produced at a rate corresponding to a mass conversion rate of interstellar grains of between 2% and 20% in 107 yr. The shape and position of the astronomically observed 3.1 m band is duplicated in the laboratory and is shown to be a natural consequence of the processing of grain mantles.Invited contribution to the Proceedings of a Workshop onThermodynamics and Kinetics of Dust Formation in the Space Medium held at the Lunar and Planetary Institute, Houston, 6–8 September, 1978. 相似文献
13.
The contraction of an interstellar cloud is followed. The results indicates that there are shock waves appear during contraction. In order to study the effect of shock waves, two models have been studied. The post-shock temperature for the two models are, respectively, 3006 K and 2984 K. The density increases by more than three orders of magnitude. The gas is generally cooled by atoms, molecules, and grains. The dominant cooling process changes according to the chemical composition and the temperature of the gas. The thermal equilibrium depends on the existing physical conditions. 相似文献
14.
15.
For the laboratory astrophysics community,those spectroscopic modeling codes extensively used in astronomy,e.g.Chianti,AtomDB,Cloudy and Xstar,cannot be directly applied to analyzing laboratory measurements due to their discrepancies from astrophysical cases.For example,plasma from an electron beam ion trap has an electron energy distribution that follows a Gaussian profile,instead of a Maxwellian one.The laboratory miniature for a compact object produced by a laser-driven implosion shows a departure from equilibrium,that often occurs in celestial objects,so we setup a spectral analysis system for astrophysical and laboratory(sasal) plasmas to act as a bridge between them,which benefits the laboratory astrophysical community. 相似文献
16.
A number of small, cyclic molecules containing several carbon atoms in their ring structure has been identified in different astrophysical environments. It is the aim of this work to study important molecular properties of such heterocyclic species bearing an iron atom, which is one of the most abundant cosmic elements. Quantum theoretical calculations based on a density functional approach have been employed to investigate physical properties of six small cyclic carbon and hydrocarbon molecules containing iron as a hetero atom, viz. FeC2H n and FeC3H n (n=0,2,4). The full geometry optimisation at the chosen level of electronic structure theory (B3LYP/6-31G(d)) including vibrational anharmonicities and non-rigidity, has furnished values for the rotational constants of these species to an expected accuracy of about one per cent. We present structural, electronic, vibrational, and rotational molecular properties including line frequencies, line strengths, and transition probabilities. These results may be helpful for identifying these molecules in future laboratory experiments in view of tentative astronomical observations. 相似文献
17.
Similarity theory, which is necessary in order to apply the results of laboratory astrophysics experiments to relativistic
astrophysical plasmas, is presented. The analytical predictions of the similarity theory are compared with PIC numerical simulations
and the most recent experimental data on monoenergetic electron acceleration in diluted plasmas and high harmonic generation
at overdense plasma boundaries. We demonstrate that similarity theory is a reliable tool for explaining a surprisingly wide
variety of laboratory plasma phenomena the predictions of which can be scaled up to astrophysical dimensions. 相似文献
18.
A. Baudry J. Brillet J. M. Desbats J. Lacroix G. Montignac P. Encrenaz R. Lucas G. Beaudin P. Dierich A. Germont P. Landry G. Rerat 《Journal of Astrophysics and Astronomy》1980,1(2):193-196
A new millimeter-wave facility is in operation at the Bordeaux Observatory for spectroscopic observations of interstellar
and stratospheric molecules. A cooled receiver has been installed on a 2·5m radio telescope. The overall system temperature
is in the range 400 to 600 K (single side band) in the operating frequency range 75 to 115 GHz. The relatively broad beam
of the telescope (∼ 5 arcmin) combined with a sensitive receiver will permit studies of extended molecular cloud complexes. 相似文献
19.
M. Rosenberg 《Astrophysics and Space Science》2001,277(1-2):125-133
Ionized gases containing fine (μm to sub-μm sized) charged dust grains, referred to as dusty plasmas, occur in diverse cosmic
and laboratory environments. Dust occurs in many space and astrophysical environments, including planetary rings, comets,
the Earth's ionosphere, and interstellar molecular clouds. Dust also occurs in laboratory plasmas, including processing plasmas,
and crystallized dusty plasmas. Charged dust can lead to various effects in a plasma. In this review, some physical processes
in dusty plasmas are discussed, with an emphasis on applications to dusty plasmas in space. This includes theoretical work
on several wave instabilities, the role of dust as an electron source, and Coulomb crystals of positively charged dust.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
20.
The existence of the polyynes — molecules consisting essentially of long chains of carbon atoms — in the interstellar medium is a discovery that appears to be critical to our understanding of interstellar chemistry. The family relationships of these species to other interstellar species are explored as are their significance to theories of interstellar chemistry. Methods for deducing the numbers of related molecules are presented. 相似文献