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An essential requisite for the appearance and permanence of life on Earth is the onset of a continuous “cycling” of some key atoms and molecules. Cycling of elements probably also occurs on other objects and is driven by biological or a-biological processing. Here we investigate the cycling of some species in the icy Galilean satellites that are exposed to the intense fluxes of energetic particles coming from the Jupiter magnetosphere. Among the most studied effects of particle bombardment, there is the production of molecules not originally present in the sample. These newly synthesized species are irradiated as well and in some circumstances can re-form the original species, giving rise to a “cycle”. Here we discuss the cycling of some atoms (C, N, O, S) incorporated in molecules observed on the surface of the icy Galilean satellites. The results indicate that cycling of carbon atoms starts with solid elemental carbon. Irradiated in the presence of water ice, carbon dioxide is produced and forms carbonic acid and other organics whose irradiation re-produces carbon dioxide and solid carbon. The effect on nitrogen atoms is limited to a continuous cycle among nitrogen oxides (e.g. NO2 produces NO, and N2O). Oxygen is mostly incorporated in water ice. When irradiated, the large majority of the water molecular fragments recombine to re-form water molecules. The sulfur cycle occurs among SO2 (that cannot be produced by ion irradiation only), sulfuric acid and elemental sulfur. The results are discussed in view of their relevance to the expected space observations of the JWST telescope (NASA, ESA, CSA) and the JUICE (ESA) spacecraft. [ABSTRACT FROM AUTHOR]

Inter- and circumstellar ices comprise different molecules accreted on cold dust particles. These icy dust grains provide a molecule reservoir where particles can interact and react. As the grain acts as a third body, capable of absorbing energy, icy surfaces in space have a catalytic effect. Chemical reactions are triggered by a number of possible processes; (i) irradiation by light, typically UV photons from the interstellar radiation field and Ly- α radiation emitted by excited hydrogen, but also X-rays, (ii) bombardment by particles, free atoms (most noticeably hydrogen, but also N, C, O and D-atoms), electrons, low energy ions and cosmic rays, and (iii) thermal processing. All these effects cause ices to (photo)desorb, induce fragmentation or ionization in the ice, and eventual recombination will make molecules to react and to form more and more complex species. The effects of this solid state astrochemistry are observed by astronomers; nearly 180 different molecules (not including isotopologues) have been unambiguously identified in the inter- and circumstellar medium, and the abundances of a substantial part of these species cannot be explained by gas phase reaction schemes only and must involve solid state chemistry. Icy dust grains in space experience different chemical stages. In the diffuse medium grains are barely covered by molecules, but upon gravitational collapse and darkening of the cloud, temperatures drop and dust grains start acting as micrometer sized cryopumps. More and more species accrete, until even the most volatile species are frozen. In parallel (non)energetic processing can take place, particularly during planet and star formation when radiation and particle fluxes are intense. The physical and chemical properties of ice clearly provide a snapshotroot to characterize the cosmological chemical evolution. In order to fully interpret the astronomical observations, therefore, dedicated laboratory experiments are needed that simulate dust grain formation and processing as well as ice mantle chemistry under astronomical conditions and in full control of the relevant parameters; ice morphology (i.e., structure), composition, temperature, UV and particle fluxes, etc., yielding parameters that can be used for astrochemical modeling and for comparison with the observations. This is the topic of the present manuscript. Laboratory experiments simulating the conditions in space are conducted for decades all over the world, but particularly in recent years new techniques have made it possible to study reactions involving inter- and circumstellar dust and ice analogues at an unprecedented level of detail. Whereas in the past “top-down scenarios” allowed to conclude on the importance of the solid state for the chemical enrichment of space, presently “bottom-up approaches” make it possible to fully quantify the involved reactions, and to provide information on processes at the molecular level. The recent progress in the field of “solid state laboratory astrophysics” is a consequence of the use of ultra high vacuum systems, of new radiation sources, such as synchrotrons and laser systems that allow extensions to wavelength domains that long have not been accessible, including the THz domain, and the use of highly sensitive gas phase detection techniques, explicitly applied to characterize the solid state such as fluorescence, luminescence, cavity ring-down spectroscopy and sophisticated mass spectrometric techniques. This paper presents an overview of the techniques being used in astrochemical laboratories worldwide, but it is incomplete in the sense that it summarizes the outcome of a 3-day workshop of the authors in November 2012 (at the Observatoire de Meudon in France), with several laboratories represented, but not all. The paper references earlier work, but it is incomplete with regard to latest developments of techniques used in laboratories not represented at the workshop. [ABSTRACT FROM AUTHOR]

Using a genetic algorithm together with DFT computations, the stable isomers of Lin+1Fn (n = 2 ~ 17) are obtained. It is found that the Li3F2 is a planar structure, and starting at n = 3, Lin+1Fn adopt three-dimensional configurations with a terminal Li atom or vacancy of F atom. As the cluster sizes increase, the geometries of Lin+1Fn develop, first with cube-like and tubular structures, then forming cage-like arrangements, and eventually favoring rock-salt configurations. The Lin+1Fn (n = 3, 5, 8, 11, 13 and 15) are especially stable and magic number clusters. Low ionization potentials are acquired for Lin+1Fn due to the weakly bonded odd electrons of Li atoms. Particularly, the AIP/VIP for Li14F13 and Li17F16 are only 2.68/2.75 eV and 2.77/2.97 eV, respectively, which indicate that they can be looked as superalkali clusters. Meanwhile, the particularly large hyperpolarizabilities (3237157.14 a.u. and 716489.10 a.u.) for these two isomers are also obtained. According to the electronic structure analysis, Li atoms donate their 2s electrons to the 2p orbitals of F atoms, forming Li–F ionic bonds. Additionally, the spectral properties and the reactivities for the magic number clusters are further investigated. [ABSTRACT FROM AUTHOR]

Ar ion beam collisions at 105 kev on He and molecular hydrogen targets are studied by photon spectroscopy. New transitions of the Ar and Ar spectra due to single and double electron captures are observed and interpreted through ab initio calculations. [ABSTRACT FROM AUTHOR]

The pyrolytic fuel generated by high-density polyethylene (HDPE) has the potential to replace fossil fuels as a primary source of energy. Thermal pyrolysis of HDPE had been performed in a stainless-steel batch reactor having a height of 300 mm, inner diameter 200 mm, and maximum liquid yield was found as 69.33% for an optimum temperature of 500 ℃ in presence of nitrogen as carrier gas. The pyrolytic liquid was composed of mostly alkanes and alkenes and has a high calorific value of 41.5 MJ/kg. The waste plastics of HDPE were blended with virgin plastics to compare the liquid product yield and optimize the process condition. The optimal pyrolysis condition had been determined by response surface methodology (RSM) in combination with central composite design (CCD). The regression equation and analysis of variance were found using Design–Expert Software and F value (82.59) and p value (< 0.0001) for optimized model indicates that the model is fitted extremely well. Both thermal pyrolysis of virgin and waste plastics produce significant amounts of liquid. The huge plastic waste accumulated at various landfill sites can be effectively reduced by the application of this process. [ABSTRACT FROM AUTHOR]

The Moon and Mercury are airless bodies, thus they are directly exposed to the ambient plasma (ions and electrons), to photons mostly from the Sun from infrared range all the way to X-rays, and to meteoroid fluxes. Direct exposure to these exogenic sources has important consequences for the formation and evolution of planetary surfaces, including altering their chemical makeup and optical properties, and generating neutral gas exosphere. The formation of a thin atmosphere, more specifically a surface bound exosphere, the relevant physical processes for the particle release, particle loss, and the drivers behind these processes are discussed in this review. [ABSTRACT FROM AUTHOR]

In this work, we investigated the formation of protonated hydrogen cyanide HCNH+ and methylene amine cation CH 2 NH 2 + (both identified in Titan's upper atmosphere) from three different pathways which stem from the interaction between CH4 and N+(3P). As a mechanistic tool, we used the Unified Reaction Valley Approach (URVA) complemented with the Local Mode Analysis (LMA) assessing the strength of the CN bonds formed in these reactions. Our URVA studies could provide a comprehensive overview on bond formation/cleavage processes relevant to the specific mechanism of eight reactions R1– R8 that occur across the three pathways. In addition, we could explain the formation of CH 2 NH 2 + and the appearance of HCNH+ and CHNH 2 + along these paths. Although only smaller molecules are involved in these reactions including isomerization, hydrogen atom abstraction, and hydrogen molecule capture, we found a number of interesting features, such as roaming in reaction R3 or the primary interaction of H2 with the carbon atom in HCNH+ in reaction R8 followed by migration of one of the H2 hydrogen atoms to the nitrogen which is more cost effective than breaking the HH bond first; a feature often found in catalysis. In all cases, charge transfer between carbon and nitrogen could be identified as a driving force for the CN bond formation. As revealed by LMA, the CN bonds formed in reactions R1–R8 cover a broad bond strength range from very weak to very strong, with the CN bond in protonated hydrogen cyanide HCNH+ identified as the strongest of all molecules investigated in this work. Our study demonstrates the large potential of both URVA and LMA to shed new light into these extraterrestrial reactions to help better understand prebiotic processes as well as develop guidelines for future investigations involving areas of complex interstellar chemistry. In particular, the formation of CN bonds as a precursor to the extraterrestrial formation of amino acids will be the focus of future investigations. [ABSTRACT FROM AUTHOR]

Sulfur is the tenth most abundant element in the universe and is known to play a significant role in biological systems. Accordingly, in recent years there has been increased interest in the role of sulfur in astrochemical reactions and planetary geology and geochemistry. Among the many avenues of research currently being explored is the laboratory processing of astrophysical ice analogues. Such research involves the synthesis of an ice of specific morphology and chemical composition at temperatures and pressures relevant to a selected astrophysical setting (such as the interstellar medium or the surfaces of icy moons). Subsequent processing of the ice under conditions that simulate the selected astrophysical setting commonly involves radiolysis, photolysis, thermal processing, neutral-neutral fragment chemistry, or any combination of these, and has been the subject of several studies. The in-situ changes in ice morphology and chemistry occurring during such processing are often monitored via spectroscopic or spectrometric techniques. In this paper, we have reviewed the results of laboratory investigations concerned with sulfur chemistry in several astrophysical ice analogues. Specifically, we review (i) the spectroscopy of sulfur-containing astrochemical molecules in the condensed phase, (ii) atom and radical addition reactions, (iii) the thermal processing of sulfur-bearing ices, (iv) photochemical experiments, (v) the non-reactive charged particle radiolysis of sulfur-bearing ices, and (vi) sulfur ion bombardment of and implantation in ice analogues. Potential future studies in the field of solid phase sulfur astrochemistry are also discussed in the context of forthcoming space missions, such as the NASA James Webb Space Telescope and the ESA Jupiter Icy Moons Explorer mission. [ABSTRACT FROM AUTHOR]

Sputtering experiments were performed by irradiating LiF, NaCl, and RbCl crystals with various swift heavy ions like S, Ni, I, Au with energies between 60 and 210 MeV, C60 clusters between 12 and 30 MeV or Pb ions between 730 and 6040 MeV. Sputtered species are collected on arc-shaped catchers and subsequently analyzed by elastic recoil detection analysis or Rutherford backscattering analysis. The study focuses on angular distributions and total yields for LiF and covers a broad range of experimental parameters including cleaved or rough sample surfaces, ion fluence, beam incident angles, and different ion velocities leading to electronic energy loss (Se) values from 5 to 45 keV/nm. In most cases, the angular distribution has two components, a jet-like peak perpendicular to the surface sample superimposed on a broad isotropic cosine distribution whatever is the beam incident angle. The observation of the jet depends mainly on the surface flatness and angle of ion incidence. However, the jet does not appear clearly when irradiated with C60 cluster. The sputtering yield is stoichiometric and characterized by huge total yields of up to a few 105 atoms per incident ion. The yield follows a power law as function of electronic energy loss, Y follows an exponential law with Sen with n ~ 4. While the azimuthal symmetry for sputtering is observed at low ion velocity (~1 MeV/u), it seems to be lost at high velocity (>4 MeV/u). The data provide a comprehensive overview how the angular distribution and the total sputtering yield scale with the energy loss, beam incidence angle and ion velocity. Complementary experiments have been done with NaCl and RbCl targets confirming the observation made for LiF. [ABSTRACT FROM AUTHOR]

BepiColombo has a larger and in many ways more capable suite of instruments relevant for determination of the topographic, physical, chemical and mineralogical properties of Mercury's surface than the suite carried by NASA's MESSENGER spacecraft. Moreover, BepiColombo's data rate is substantially higher. This equips it to confirm, elaborate upon, and go beyond many of MESSENGER's remarkable achievements. Furthermore, the geometry of BepiColombo's orbital science campaign, beginning in 2026, will enable it to make uniformly resolved observations of both northern and southern hemispheres. This will offer more detailed and complete imaging and topographic mapping, element mapping with better sensitivity and improved spatial resolution, and totally new mineralogical mapping. We discuss MESSENGER data in the context of preparing for BepiColombo, and describe the contributions that we expect BepiColombo to make towards increased knowledge and understanding of Mercury's surface and its composition. Much current work, including analysis of analogue materials, is directed towards better preparing ourselves to understand what BepiColombo might reveal. Some of MESSENGER's more remarkable observations were obtained under unique or extreme conditions. BepiColombo should be able to confirm the validity of these observations and reveal the extent to which they are representative of the planet as a whole. It will also make new observations to clarify geological processes governing and reflecting crustal origin and evolution. We anticipate that the insights gained into Mercury's geological history and its current space weathering environment will enable us to better understand the relationships of surface chemistry, morphologies and structures with the composition of crustal types, including the nature and mobility of volatile species. This will enable estimation of the composition of the mantle from which the crust was derived, and lead to tighter constraints on models for Mercury's origin including the nature and original heliocentric distance of the material from which it formed. [ABSTRACT FROM AUTHOR]

The RNA nucleosides, namely adenosine, cytidine, guanosine and uridine were γ-radioyzed in solid state and in vacuo at room temperature to a total dose of 3.2 MGy. Through electronic absorption spectroscopy, differential scanning calorimetry and through polarimetry and optical rotatory dispersion spectroscopy, it was found that the purine-based nucleosides (adenosine and guanosine) show a much higher radiolysis resistance than the pyrimidine-based nucleosides (cytidine and uridine). In an astrochemical/astrobiological context, these results may explain why purine nucleobases are found in practically all carbonaceous chondrite meteorites while the pyrimidine nucleobases are absent or below the detection limits of the current analytical techniques. In the hypothesis that both purines and pyrimidines nucleobases were present in certain bodies at the beginning of the solar system 4.6 × 109 years ago, the radiolysis due to radionuclides decay has destroyed more easily and completely the pyrimidine bases due to their much lower radiolysis resistance than the purine bases. [ABSTRACT FROM AUTHOR]

We theoretically improved the relativistic ADK formula for a linearly polarized laser field. We have taken into account the influence of the magnetic component of laser field on the transition rate, in near relativistic field intensity. It was shown that the magnetic component results in a decrease of the transition rate in comparison to the results obtained by the original relativistic expression. We gave considered noble and alkali atoms. The obtained results show that this influence is larger (more significant) for alkali atoms. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO) and carbon disulphide (CS) molecular ice mixture was prepared under low temperature (85 K) astrochemical conditions. The icy mixture irradiated with keV electrons simulates the irradiation environment experienced by icy satellites and Interstellar Icy Mantles (IIM). Upon electron irradiation the chemical composition was found to have altered and the new products from irradiation were found to be carbonyl sulphide (OCS), sulphur dioxide (SO), ozone (O), carbon trioxide (CO), sulphur trioxide (SO), carbon subsulphide (C S) and carbon monoxide (CO). Results obtained confirm the presence of CS molecules in lunar south-pole probed by the Moon Impact Probe (MIP). [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Astrochemistry is the discipline that studies physico-chemical processes in astrophysical environments. Such environments are characterized by conditions that are substantially different from those existing in usual chemical laboratories. Models which aim to explain the formation of molecular species in interstellar environments must take into account various factors, including many that are directly, or indirectly related to the populations of massive stars in galaxies. The aim of this paper is to review the influence of massive stars, whatever their evolution stage, on the physico-chemical processes at work in interstellar environments. These influences include the ultraviolet radiation field, the production of high energy particles, the synthesis of radionuclides and the formation of shocks that permeate the interstellar medium. [ABSTRACT FROM AUTHOR]

Our Sun and planetary system were born about 4.5 billion years ago. How did this happen, and what is the nature of our heritage from these early times? This review tries to address these questions from an astrochemical point of view. On the one hand, we have some crucial information from meteorites, comets and other small bodies of the Solar System. On the other hand, we have the results of studies on the formation process of Sun-like stars in our Galaxy. These results tell us that Sun-like stars form in dense regions of molecular clouds and that three major steps are involved before the planet-formation period. They are represented by the prestellar core, protostellar envelope and protoplanetary disk phases. Simultaneously with the evolution from one phase to the other, the chemical composition gains increasing complexity. In this review, we first present the information on the chemical composition of meteorites, comets and other small bodies of the Solar System, which is potentially linked to the first phases of the Solar System's formation. Then we describe the observed chemical composition in the prestellar core, protostellar envelope and protoplanetary-disk phases, including the processes that lead to them. Finally, we draw together pieces from the different objects and phases to understand whether and how much we inherited chemically from the time of the Sun's birth. [ABSTRACT FROM AUTHOR]

This presentation considers how the interaction between physical conditions in plasmas and atomic-structure properties affects the role played by highly-charged ions. It is emphasised that reliable and accurate atomic data are required to determine plasma conditions from the analysis of spectral line intensities. Atomic-structure problems which limit the quality of available atomic data are discussed. Spectroscopic observations quoted provide information on the behaviour of ions in plasmas. [ABSTRACT FROM AUTHOR]

Visible light emission spectra during collisions between O5+ ions and He atoms in the range of 200–800 nm at different projectile energies (4.06–5.31 keV-u−1) have been measured. Emission spectra show that there are three channels of excitation in the O5+-He collision system: (i) single-electron capture into excited states; (ii) double-electron capture into excited states; (iii) direct excitation of target atoms. There are transitions between states with comparably high quantum numbers nl. The absolute emission cross-sections of every spectral line are calculated. The relations of these cross-sections with the energy of the projectiles are studied. [ABSTRACT FROM AUTHOR]

We report the results of laboratory measurements of H2O2 production inside thin (50 nm thickness) H2O and H2O:O2 ice samples irradiated by 121.6 nm photons at different temperatures. In the case of H2O ice, H2O2 is formed at the temperatures below 60 К. In the case of H2O:O2 ice, H2O2 is formed in the 20–140 К range. For H2O:O2 = 9:1 ice, we derived H2O2 photochemical quantum yield as a function of sample irradiation temperature. The obtained data can be used for evaluation of H2O2 photoproduction at the surface of astrophysical water ice bodies and inside the particles of Noctilucent Clouds in the Earth's atmosphere. [ABSTRACT FROM AUTHOR]

Interplanetary dust particles and meteoroids mostly originate from comets and asteroids. Understanding their distribution in the Solar system, their dynamical behavior and their properties, sheds light on the current state and the dynamical behavior of the Solar system. Dust particles can endanger Earth-orbiting satellites and deep-space probes, and a good understanding of the spatial density and velocity distribution of dust and meteoroids in the Solar system is important for designing proper spacecraft shielding. The study of interplanetary dust and meteoroids provides clues to the formation of the Solar system. Particles having formed 4.5 billion years ago can survive planetary accretion and those that survived until now did not evolve significantly since then. Meteoroids and interplanetary dust can be observed by measuring the intensity and polarization of the zodiacal light, by observing meteors entering the Earth's atmosphere, by collecting them in the upper atmosphere, polar ices and snow, and by detecting them with in-situ detectors on space probes. [ABSTRACT FROM AUTHOR]