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Articoli di riviste sul tema "Astrophysical ices"

Autore: Grafiati

Pubblicato: 11 gennaio 2025

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1

Palumbo, M. E., G. A. Baratta, D. Fulvio, M. Garozzo, O. Gomis, G. Leto, F. Spinella e G. Strazzulla. "Ion irradiation of astrophysical ices". Journal of Physics: Conference Series 101 (1 febbraio 2008): 012002. http://dx.doi.org/10.1088/1742-6596/101/1/012002.

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Palumbo, M. E., G. A. Baratta, G. Leto e G. Strazzulla. "H bonds in astrophysical ices". Journal of Molecular Structure 972, n. 1-3 (maggio 2010): 64–67. http://dx.doi.org/10.1016/j.molstruc.2009.12.017.

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3

Boduch, Philippe, Emmanuel Dartois, Ana L. F. de Barros, Enio F. da Silveira, Alicja Domaracka, Xue-Yang Lv, Maria Elisabetta Palumbo et al. "Radiation effects in astrophysical ices". Journal of Physics: Conference Series 629 (13 luglio 2015): 012008. http://dx.doi.org/10.1088/1742-6596/629/1/012008.

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4

Strazzulla, G., A. C. Castorina e M. E. Palumbo. "Ion irradiation of astrophysical ices". Planetary and Space Science 43, n. 10-11 (ottobre 1995): 1247–51. http://dx.doi.org/10.1016/0032-0633(95)00040-c.

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5

Farenzena, L. S., P. Iza, R. Martinez, F. A. Fernandez-Lima, E. Seperuelo Duarte, G. S. Faraudo, C. R. Ponciano et al. "Electronic Sputtering Analysis of Astrophysical Ices". Earth, Moon, and Planets 97, n. 3-4 (dicembre 2005): 311–29. http://dx.doi.org/10.1007/s11038-006-9081-y.

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6

Golikov, O., D. Yerezhep, A. Akylbayeva, D. Sokolov, E. Korshikov e A. Aldiyarov. "Cryovacuum facilities for studying astrophysical ices". Low Temperature Physics 50, n. 1 (1 gennaio 2024): 66–72. http://dx.doi.org/10.1063/10.0023894.

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This work introduces a cryovacuum apparatus used to investigate substances under near-space conditions. This device allows one to study the refractive index, infrared spectra, and density of substances that are condensed from the vapor phase onto a cooled substrate at temperatures ranging from 11 K to 300 K. Concurrently, the ultimate pressure of 0.1 nTorr can be obtained in the vacuum chamber. The introduced setup utilizes FTIR spectroscopy with a spectral measurement range of 400–7800 cm−1 and laser interference needed to determine the important physical and optical parameters. Several experiments allow us to stress that the data acquired using this apparatus are quite similar to those obtained by other researchers. Because of the non-directional deposition of substances from the vapor phase, the ice formed closely resembles the ice formed in space. This makes the introduced setup particularly useful. It is possible to use the presented cryovacuum apparatus to interpret data acquired in the course of astrophysical observations, allowing a researcher to determine the properties of space objects.

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Moore, Marla H., e Reggie L. Hudson. "Production of Complex Molecules in Astrophysical Ices". Proceedings of the International Astronomical Union 1, S231 (21 marzo 2006): 247. http://dx.doi.org/10.1017/s1743921306007241.

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8

Rocard, F., J. Bénit, J.-P. Bibrtng, D. Ledu e R. Meunier. "Erosion of ices: Physical and astrophysical discussion". Radiation Effects 99, n. 1-4 (settembre 1986): 97–104. http://dx.doi.org/10.1080/00337578608209617.

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9

Strazzulla, G. "Crystalline and amorphous structure of astrophysical ices". Low Temperature Physics 39, n. 5 (maggio 2013): 430–33. http://dx.doi.org/10.1063/1.4807045.

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10

Förstel, M., P. Maksyutenko, B. M. Jones, B. J. Sun, A. H. H. Chang e R. I. Kaiser. "Synthesis of urea in cometary model ices and implications for Comet 67P/Churyumov–Gerasimenko". Chemical Communications 52, n. 4 (2016): 741–44. http://dx.doi.org/10.1039/c5cc07635h.

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11

Rocha, W. R. M., M. G. Rachid, B. Olsthoorn, E. F. van Dishoeck, M. K. McClure, K. Slavicinska e H. Linnartz. "SPECFY - an important tool of the Leiden Ice Database for Astrochemistry in the era of the James Webb Space Telescope". Proceedings of the International Astronomical Union 18, S371 (agosto 2022): 67–71. http://dx.doi.org/10.1017/s174392132300039x.

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AbstractMolecular data obtained from laboratory studies are crucial for deriving chemical abundances in astrophysical environments. The Leiden Ice Database for Astrochemistry (LIDA; https://icedb.strw.leidenuniv.nl/) has supported these studies for years in the context of astrophysical ices. For the era of the James Webb Space Telescope - JWST, LIDA hosts more than 1100 infrared spectra of pure and mixed ices that mimic different astrophysical conditions and UV-vis optical constants of water ice. Additionally, LIDA has an online tool - SPECFY, that allows the creation of protostar synthetic spectra. In this paper, we create a synthetic spectrum including OCS ice to check the detection feasibility of this molecule with a 3σ significance using JWST. The calculations are made with the exposure time calculator (ETC). LIDA is a prime deliverable of Ice Age, an Early Release Science JWST program. The collected data and online tools are also accessible for other programs collecting ice data.

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12

Nuevo, Michel, George Cooper, John M. Saunders, Christina E. Buffo e Scott A. Sandford. "Formation of complex organic molecules in astrophysical environments: Sugars and derivatives". Proceedings of the International Astronomical Union 15, S350 (aprile 2019): 123–26. http://dx.doi.org/10.1017/s1743921319009323.

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AbstractCarbonaceous meteorites contain a large variety of complex organic molecules, including amino acids, nucleobases, sugar derivatives, amphiphiles, and other compounds of astrobiological interest. Photoprocessing of ices condensed on cold grains with ultraviolet (UV) photons was proposed as an efficient way to form such complex organics in astrophysical environments. This hypothesis was confirmed by laboratory experiments simulating photo-irradiation of ices containing H2O, CH3OH, CO, CO2, CH4, H2CO, NH3, HCN, etc., condensed on cold (~10–80 K) substrates. These experiments resulted in the formation of amino acids, nucleobases, sugar derivatives, amphiphilic compounds, and other organics comparable to those identified in carbonaceous meteorites. This work presents results for the formation of sugars, sugar alcohols, sugar acids, and their deoxy variants from the UV irradiation of ices containing H2O and CH3OH in relative proportions 2:1, and their comparison with meteoritic data. The formation mechanisms of these compounds and the astrobiological implications are also discussed.

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13

Maté, B., G. Molpeceres, V. Timón, I. Tanarro, R. Escribano, J. C. Guillemin, J. Cernicharo e V. J. Herrero. "Laboratory study of methyl isocyanate ices under astrophysical conditions". Monthly Notices of the Royal Astronomical Society 470, n. 4 (12 giugno 2017): 4222–30. http://dx.doi.org/10.1093/mnras/stx1461.

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Fray, N., e B. Schmitt. "Sublimation of ices of astrophysical interest: A bibliographic review". Planetary and Space Science 57, n. 14-15 (dicembre 2009): 2053–80. http://dx.doi.org/10.1016/j.pss.2009.09.011.

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15

Pilling, Sergio, Geanderson A. Carvalho e Will R. M. Rocha. "Chemical Evolution of CO₂ Ices under Processing by Ionizing Radiation: Characterization of Nonobserved Species and Chemical Equilibrium Phase with the Employment of PROCODA Code". Astrophysical Journal 925, n. 2 (1 febbraio 2022): 147. http://dx.doi.org/10.3847/1538-4357/ac3d8a.

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Abstract Astrophysical ices are being exposed to ionizing radiation in space environments, which trigger new reactions and desorption processes. In the lab, such processing by radiation has revealed the appearance of several new species and complements the study of the chemical evolution of icy astrophysical scenarios. Here, we develop a computational methodology that helps to clarify the chemical evolution of ices investigated experimentally under photolysis/radiolysis processes until reaching chemical equilibrium (CE). Briefly, the code (named PROCODA) solves a system of coupled differential equations and describes the evolution of the molecular abundances with the irradiation time for ices under processing by radiation. Two experimental ice samples containing pure CO2 and irradiated by two ionizing agents (cosmic rays and ultraviolet photons) were considered prototype systems. Here, we considered 11 different chemical species within the ice (four observed: CO2, CO, O3, and CO3; seven nonobserved or unknown: O, O2, C, C2, C2O, C2O2, and C2O3), 100 reaction routes (e.g., direct dissociation reactions, bimolecular and termolecular reactions) and radiation-induced desorption processes. The best-fit models provide the reaction rates, several desorption parameters, as well as the characterization of the CE phase. At CE, the percentage of nonobserved species in the UV model was almost triple the one calculated in the CR model (which also includes a lot of O and C atoms). The determined values can be employed in future astrochemical models to map chemical evolution embedded species in astrophysical regions under the presence of an ionizing radiation field.

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16

Butscher, Teddy, Fabrice Duvernay, Albert Rimola, Mireia Segado-Centellas e Thierry Chiavassa. "Radical recombination in interstellar ices, a not so simple mechanism". Physical Chemistry Chemical Physics 19, n. 4 (2017): 2857–66. http://dx.doi.org/10.1039/c6cp07024h.

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Formyl radical reactivity has been studied under astrophysical-like conditions, showing that its dimerization does not lead to glyoxal formation. It has also been shown that its reactivity could form glyceraldehyde and formaldehyde oligomers.

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17

Ribeiro, F. de A., G. C. Almeida, Y. Garcia-Basabe, W. Wolff, H. M. Boechat-Roberty e M. L. M. Rocco. "Non-thermal ion desorption from an acetonitrile (CH3CN) astrophysical ice analogue studied by electron stimulated ion desorption". Physical Chemistry Chemical Physics 17, n. 41 (2015): 27473–80. http://dx.doi.org/10.1039/c5cp05040e.

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Non-thermal desorption by electron impact constitutes an important route by which neutral and ionic fragments from simple nitrile-bearing ices may be delivered back to the gas-phase of astrophysical environments, contributing to the production of more complex molecules.

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Jiménez-Escobar, Antonio, Angela Ciaravella, Cesare Cecchi-Pestellini, Guillermo M. Muñoz Caro, Chao-Hui Huang, Ni-En Sie e Yu-Jung Chen. "X-Ray-induced Diffusion and Mixing in Layered Astrophysical Ices". Astrophysical Journal 926, n. 2 (1 febbraio 2022): 176. http://dx.doi.org/10.3847/1538-4357/ac4810.

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Abstract Ice in cold cosmic environments is expected to be organized in a bilayered structure of polar and apolar components. The initial water-rich layer is embedded in an icy CO envelope, which provides the feedstock for methanol formation through hydrogenation. These two components are thought to be physically segregated, unless an increase in temperature favors mobility and reactivity within the ice. We present new and robust evidence of X-ray-induced diffusion within interstellar ice analogues at very low temperatures, leading to an efficient mixing of the molecular content of the ice. The results of our study have two main implications. First, molecular mixing enhances chemical reactions from which complex organic species, including many of prebiotic interest, are formed. Second, diffusion drives the desorption of species that would otherwise remain buried near the surface of dust, thus enhancing their abundances in the gas, where they can be detected in the radio-wave domain. Such a scenario may have implications for the chemical history of ices in protoplanetary disks, in particular in the early stages of their life.

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19

Luna, R., M. Á. Satorre, C. Santonja e M. Domingo. "New experimental sublimation energy measurements for some relevant astrophysical ices". Astronomy & Astrophysics 566 (giugno 2014): A27. http://dx.doi.org/10.1051/0004-6361/201323249.

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20

Loeffler, M. J., B. D. Teolis e R. A. Baragiola. "A Model Study of the Thermal Evolution of Astrophysical Ices". Astrophysical Journal 639, n. 2 (20 febbraio 2006): L103—L106. http://dx.doi.org/10.1086/502969.

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21

Edridge, John L., Kati Freimann, Daren J. Burke e Wendy A. Brown. "Surface science investigations of the role of CO 2 in astrophysical ices". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 371, n. 1994 (13 luglio 2013): 20110578. http://dx.doi.org/10.1098/rsta.2011.0578.

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We have recorded reflection–absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD) data for a range of CO 2 -bearing model astrophysical ices adsorbed on a graphitic dust grain analogue surface. Data have been recorded for pure CO 2 , for CO 2 adsorbed on top of amorphous solid water, for mixed CO 2 :H 2 O ices and for CO 2 adsorbed on top of a mixed CH 3 OH:H 2 O ice. For the TPD data, kinetic parameters for desorption have been determined, and the trapping behaviour of the CO 2 in the H 2 O (CH 3 OH) ice has been determined. Data of these types are important as they can be used to model desorption in a range of astrophysical environments. RAIR spectra have also shown the interaction of the CO 2 with H 2 O and CH 3 OH and can be used to compare with astronomical observations, allowing the accurate assignment of spectra.

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22

Pilling, Sergio. "Processing of astrophysical ices by soft X-rays and swift ions". Proceedings of the International Astronomical Union 13, S332 (marzo 2017): 281–92. http://dx.doi.org/10.1017/s1743921317007840.

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AbstractThe employment of soft X-rays and swift ions has been used in laboratory to simulate the physicochemical processing of astrophysical ice analogs by energetic photons and cosmic rays. This processing includes excitation, ionization and molecular dissociation, desorption, as well as triggers the formation of new compounds. Here we present some results from experiments employing infrared spectroscopy in two different laboratories: LNLS/CNPEM in Campinas/Brazil and GANIL/CIRIL/CIMAP in Caen/France. Among the results are the formation of alkenes and aromatic compounds during the irradiation of saturated hydrocarbon-containing ices by cosmic ray analogs, the production of the nucleobase adenine during soft X-ray photolysis of N2:CH4 ice, as well as the formation of peptide bonds during the bombardment of frozen glycine by cosmic ray analogs. The interaction between cosmic ray analogs and ionizing soft X-rays probed in the laboratory allows us to identify reaction routes that lead to chemistry enhancement of astrophysical ices and help us put constrains in prebiotic chemistry.

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Jäger, Cornelia, Alexey Potapov, Gaël Rouillé e Thomas Henning. "Laboratory experiments on cosmic dust and ices". Proceedings of the International Astronomical Union 15, S350 (aprile 2019): 27–34. http://dx.doi.org/10.1017/s1743921319009682.

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AbstractThe existence of cosmic dust is attested by the interstellar extinction and polarization, IR emission and absorption spectra, and elemental depletion patterns. Dust grains are efficiently processed or even destroyed in shocks, molecular clouds, or protoplanetary disks. A considerable amount of dust has to be re-formed in the ISM. In various astrophysical environments, dust grains are covered by molecular ices and therefore contribute or catalytically influence the chemical reactions in these layers. Laboratory experiments are desperately required to understand the evolution of grains and grain/ice mixtures in molecular clouds and early planetary disks. This review considers recent progress in laboratory approaches to dust/ice experiments.

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Domaracka, A., E. Seperuelo Duarte, P. Boduch, H. Rothard, E. Balanzat, E. Dartois, S. Pilling, L. S. Farenzena e E. F. da Silveira. "Irradiation effects in CO and CO2 ices induced by swift heavy Ni ions at 46 MeV and 537 MeV". Proceedings of the International Astronomical Union 5, S265 (agosto 2009): 428–29. http://dx.doi.org/10.1017/s174392131000116x.

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AbstractIn order to simulate the effects of the heavy ion component of cosmic rays on ices in astrophysical environments, the CO and CO2 ices were irradiated with swift nickel ions in the electronic energy loss regime. The ices were prepared by condensing gas onto a CsI substrate at a temperature of 14 K and analyzed by means of infrared (FTIR) spectroscopy. The physical process of deposition by Ni ions is similar to more important and abundant heavy cosmic rays such as Fe ions. Dissociation of the ice molecules, and formation of new molecules were observed. Also, sputtering (leading to desorption of molecules from the solid surface to the gas phase) was observed. It was found that the sputtering yield due to heavy ions cannot be neglected with respect to desorption induced by weakly ionizing particles such as UV photons and protons.

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Knez, C., M. H. Moore, R. F. Ferrante e R. L. Hudson. "LABORATORY IR STUDIES AND ASTROPHYSICAL IMPLICATIONS OF C2H2-CONTAINING BINARY ICES". Astrophysical Journal 748, n. 2 (13 marzo 2012): 95. http://dx.doi.org/10.1088/0004-637x/748/2/95.

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Leroux, Killian, e Lahouari Krim. "Thermal and photochemical study of CH3OH and CH3OH–O2 astrophysical ices". Monthly Notices of the Royal Astronomical Society 500, n. 1 (20 ottobre 2020): 1188–200. http://dx.doi.org/10.1093/mnras/staa3205.

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ABSTRACT Methanol, which is one of the most abundant organic molecules in the interstellar medium, plays an important role in the complex grain surface chemistry that is believed to be a source of many organic compounds. Under energetic processing such as ultraviolet (UV) photons or cosmic rays, methanol may decompose into CH4, CO2, CO, HCO, H2CO, CH3O and CH2OH, which in turn lead to complex organic molecules such as CH3OCHO, CHOCH2OH and HOCH2CH2OH through radical recombination reactions. However, although molecular oxygen and its detection, abundance and role in the interstellar medium have been the subject of many debates, few experiments on the oxidation of organic compounds have been carried out under interstellar conditions. The present study shows the behaviour of solid methanol when treated by UV light and thermal processing in oxygen-rich environments. Methanol has been irradiated in the absence and presence of O2 at different concentrations in order to study how oxidized complex organic molecules may form and also to investigate the O-insertion reaction in the C–H bound to form methanediol HOCH2OH through a CH3OH + O(1D) solid-state reaction. The adding of O2 in the thermal and photochemical reaction of solid methanol leads to the formation of O3, H2O and HO2, in addition to three main organics, HCOOH, CHOCHO and HOCH2OH. We show that in an O2-rich environment, species such as CO, CH4, HCO, CH3OH and CHOCH2OH are oxidized into CO2, CH3OH, HC(O)OO, HOCH2OH and CHOCHO, respectively, while HCOOH might be formed through the H2CO + O(3P) → (OH + HCO)cage → HCOOH hydrogen-abstraction reaction.

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Allodi, M. A., R. A. Baragiola, G. A. Baratta, M. A. Barucci, G. A. Blake, P. Boduch, J. R. Brucato et al. "Complementary and Emerging Techniques for Astrophysical Ices Processed in the Laboratory". Space Science Reviews 180, n. 1-4 (26 settembre 2013): 101–75. http://dx.doi.org/10.1007/s11214-013-0020-8.

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Bénit, J., J. P. Bibring, S. Della Negra, Y. Le Beyec e F. Rocard. "Ion desorption by high energy irradiation of ices and Astrophysical implications". Radiation Effects 99, n. 1-4 (settembre 1986): 105–13. http://dx.doi.org/10.1080/00337578608209618.

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Esmaili, Sasan, Andrew D. Bass, Pierre Cloutier, Léon Sanche e Michael A. Huels. "Synthesis of complex organic molecules in simulated methane rich astrophysical ices". Journal of Chemical Physics 147, n. 22 (14 dicembre 2017): 224704. http://dx.doi.org/10.1063/1.5003898.

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Schutte, W., L. Allamandola e S. Sandford. "Formaldehyde and organic molecule production in astrophysical ices at cryogenic temperatures". Science 259, n. 5098 (19 febbraio 1993): 1143–45. http://dx.doi.org/10.1126/science.11540093.

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Carvalho, G. A., e S. Pilling. "Time-scales to reach chemical equilibrium in ices at snowline distance around compact objects: the influence of accretion mass in the central object". Monthly Notices of the Royal Astronomical Society 503, n. 2 (5 marzo 2021): 2973–78. http://dx.doi.org/10.1093/mnras/stab641.

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ABSTRACT In this work, we analyse soft X-ray emission due to mass accretion on to compact stars and its effects on the time-scale to reach chemical equilibrium of eventual surrounding astrophysical ices exposed to that radiation. Reaction time-scales due to soft X-ray in water-rich and pure ices of methanol, acetone, acetonitrile, formic acid, and acetic acid were determined. For accretion rates in the range $\dot{m}=10^{-12}\!-\!10^{-8}\,{\rm M}_\odot$ yr−1 and distances in the range 1–3 LY from the central compact objects, the time-scales lie in the range 10–108 yr, with shorter time-scales corresponding to higher accretion rates. Obtained time-scales for ices at snow-line distances can be small when compared to the lifetime (or age) of the compact stars, showing that chemical equilibrium could have been achieved. Time-scales for ices to reach chemical equilibrium depend on X-ray flux and, hence, on accretion rate, which indicates that systems with low accretion rates may not have reached chemical equilibrium.

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Luna, Ramón, Carlos Millán, Manuel Domingo, Carmina Santonja e Miguel Á. Satorre. "Density and Refractive Index of Carbon Monoxide Ice at Different Temperatures". Astrophysical Journal 935, n. 2 (1 agosto 2022): 134. http://dx.doi.org/10.3847/1538-4357/ac8001.

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Abstract This paper is intended to study the density and the refractive index of the solid carbon monoxide in the interval 13–28 K to improve our understanding of the dynamics in the astrophysical environments where they are present. A series of deposition experiments have been performed under high vacuum conditions to study the properties of this ice under astrophysical conditions. Ice density has been experimentally calculated at different deposition temperatures of astrophysical interest, which complement the scarce values present in the literature. The refractive index has also been experimentally determined. The data have been used to obtain an experimental relationship between refractive index and density. Values of density are necessary to interpret observations of astrophysical objects or to design irradiation experiments to understand how irradiation affects ices present in these objects. The experimental relationship found between density and refractive index allows us to estimate density from a known refractive index, even for temperatures not reached using our experimental setup.

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Blake, D. F., LJ Allamandola, G. Palmer e A. Pohorille. "Analytical Electron Microscopy of Extraterrestrial Ice Analogs". Proceedings, annual meeting, Electron Microscopy Society of America 48, n. 1 (12 agosto 1990): 594–95. http://dx.doi.org/10.1017/s0424820100181737.

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The natural history of the biogenic elements H, C, N, O, P and S in the cosmos is of great interest because it is these elements which comprise all life. Material ejected from stars (or pre-existing in the interstellar medium) is thought to condense into diffuse bodies of gravitationally bound gas and dust called cold interstellar molecular clouds. Current theories predict that within these clouds, at temperatures of 10-100° K, gases (primarily H2O, but including CO, CO2, CH3OH, NH3, and others) condense onto submicron silicate grains to form icy grain mantles. This interstellar ice represents the earliest and most primitive association of the biogenic elements. Within these multicomponent icy mantles, pre-biotic organic compounds are formed during exposure to UV radiation. It is thought that icy planetesimals (such as comets) within our solar system contain some pristine interstellar material, including ices, and may have (during the early bombardment of the solar system, ∼4 Ga) carried this material to Earth.Despite the widespread occurrence of astrophysical ices and their importance to pre-biotic organic evolution, few experimental data exist which address the relevant phase equilibria and possible structural states. A knowledge of the petrology of astrophysical ice analogs will allow scientists to more confidently interpret astronomical IR observations. Furthermore, the development and refinement of procedures for analyzing ices and other materials at cryogenic temperatures is critical to the study of materials returned from the proposed Rosetta comet nucleus and Mars sample return missions.

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Tonauer, Christina M., Lilli-Ruth Fidler, Johannes Giebelmann, Keishiro Yamashita e Thomas Loerting. "Nucleation and growth of crystalline ices from amorphous ices". Journal of Chemical Physics 158, n. 14 (14 aprile 2023): 141001. http://dx.doi.org/10.1063/5.0143343.

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We here review mostly experimental and some computational work devoted to nucleation in amorphous ices. In fact, there are only a handful of studies in which nucleation and growth in amorphous ices are investigated as two separate processes. In most studies, crystallization temperatures T x or crystallization rates R JG are accessed for the combined process. Our Review deals with different amorphous ices, namely, vapor-deposited amorphous solid water (ASW) encountered in many astrophysical environments; hyperquenched glassy water (HGW) produced from μm-droplets of liquid water; and low density amorphous (LDA), high density amorphous (HDA), and very high density amorphous (VHDA) ices produced via pressure-induced amorphization of ice I or from high-pressure polymorphs. We cover the pressure range of up to about 6 GPa and the temperature range of up to 270 K, where only the presence of salts allows for the observation of amorphous ices at such high temperatures. In the case of ASW, its microporosity and very high internal surface to volume ratio are the key factors determining its crystallization kinetics. For HGW, the role of interfaces between individual glassy droplets is crucial but mostly neglected in nucleation or crystallization studies. In the case of LDA, HDA, and VHDA, parallel crystallization kinetics to different ice phases is observed, where the fraction of crystallized ices is controlled by the heating rate. A key aspect here is that in different experiments, amorphous ices of different “purities” are obtained, where “purity” here means the “absence of crystalline nuclei.” For this reason, “preseeded amorphous ice” and “nuclei-free amorphous ice” should be distinguished carefully, which has not been done properly in most studies. This makes a direct comparison of results obtained in different laboratories very hard, and even results obtained in the same laboratory are affected by very small changes in the preparation protocol. In terms of mechanism, the results are consistent with amorphous ices turning into an ultraviscous, deeply supercooled liquid prior to nucleation. However, especially in preseeded amorphous ices, crystallization from the preexisting nuclei takes place simultaneously. To separate the time scales of crystallization from the time scale of structure relaxation cleanly, the goal needs to be to produce amorphous ices free from crystalline ice nuclei. Such ices have only been produced in very few studies.

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35

Woon, D. "Ab Initio Quantum Chemical Studies of Reactions in Astrophysical Ices 2. Reactions in H2CO/HCN/HNC/H2O Ices". Icarus 149, n. 1 (gennaio 2001): 277–84. http://dx.doi.org/10.1006/icar.2000.6524.

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36

Schutte, W. A., L. J. Allamandola e S. A. Sandford. "Formation of Organic Molecules by Formaldehyde Reactions in Astrophysical Ices at Very Low Temperatures". Symposium - International Astronomical Union 150 (1992): 29–30. http://dx.doi.org/10.1017/s007418090008966x.

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Abstract (sommario):

Warm-up of astrophysical ice analogues containing formaldehyde produced organic residues in large abundances. It is argued that formaldehyde reactions at very low temperatures could be an important source of interstellar and cometary organic molecules.

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37

Rosa, Caroline Antunes, Alexandre Bergantini, Péter Herczku, Duncan V. Mifsud, Gergő Lakatos, Sándor T. S. Kovács, Béla Sulik et al. "Infrared Spectral Signatures of Nucleobases in Interstellar Ices I: Purines". Life 13, n. 11 (14 novembre 2023): 2208. http://dx.doi.org/10.3390/life13112208.

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Abstract (sommario):

The purine nucleobases adenine and guanine are complex organic molecules that are essential for life. Despite their ubiquitous presence on Earth, purines have yet to be detected in observations of astronomical environments. This work therefore proposes to study the infrared spectra of purines linked to terrestrial biochemical processes under conditions analogous to those found in the interstellar medium. The infrared spectra of adenine and guanine, both in neat form and embedded within an ice made of H2O:NH3:CH4:CO:CH3OH (10:1:1:1:1), were analysed with the aim of determining which bands attributable to adenine and/or guanine can be observed in the infrared spectrum of an astrophysical ice analogue rich in other volatile species known to be abundant in dense molecular clouds. The spectrum of adenine and guanine mixed together was also analysed. This study has identified three purine nucleobase infrared absorption bands that do not overlap with bands attributable to the volatiles that are ubiquitous in the dense interstellar medium. Therefore, these three bands, which are located at 1255, 940, and 878 cm−1, are proposed as an infrared spectral signature for adenine, guanine, or a mixture of these molecules in astrophysical ices. All three bands have integrated molar absorptivity values (ψ) greater than 4 km mol−1, meaning that they should be readily observable in astronomical targets. Therefore, if these three bands were to be observed together in the same target, then it is possible to propose the presence of a purine molecule (i.e., adenine or guanine) there.

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38

Woon, David E. "Ab Initio Quantum Chemical Studies of Reactions in Astrophysical Ices 3. Reactions of HOCH2NH2Formed in H2CO/NH3/H2O Ices". Journal of Physical Chemistry A 105, n. 41 (ottobre 2001): 9478–81. http://dx.doi.org/10.1021/jp011830h.

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39

Dupuy, R., G. Féraud, M. Bertin, X. Michaut, T. Putaud, P. Jeseck, L. Philippe et al. "The efficient photodesorption of nitric oxide (NO) ices". Astronomy & Astrophysics 606 (ottobre 2017): L9. http://dx.doi.org/10.1051/0004-6361/201731653.

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Abstract (sommario):

The study and quantification of UV photon-induced desorption of frozen molecules furthers our understanding of the chemical evolution of cold interstellar regions. Nitric oxide (NO) is an important intermediate species in both gas-phase and solid-phase chemical networks. In this work, we present quantitative measurements of the photodesorption of a pure NO ice. We used the tunable monochromatic synchrotron light of the DESIRS beamline of the SOLEIL facility near Paris to irradiate NO ices in the 6–13.6 eV range and measured desorption by quadrupole mass spectrometry. We find that NO photodesorption is very efficient, its yield being around 10-2 molecule per incident photon for UV fields relevant to the diffuse and dense interstellar medium. We discuss the extrapolation of our results to an astrophysical context and we compare photodesorption of NO to previously studied molecules.

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40

Rocha, W. R. M., e S. Pilling. "Tracking the Evolutionary Stage of Protostars through the Abundances of Astrophysical Ices". Astrophysical Journal 896, n. 1 (10 giugno 2020): 27. http://dx.doi.org/10.3847/1538-4357/ab91bd.

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41

de Barros, A. L. F., P. Boduch, A. Domaracka, H. Rothard e E. F. da Silveira. "Radiolysis of astrophysical ices by heavy ion irradiation: Destruction cross section measurement". Low Temperature Physics 38, n. 8 (agosto 2012): 759–65. http://dx.doi.org/10.1063/1.4743476.

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42

Rosu-Finsen, Alexander, Jérôme Lasne, Andrew Cassidy, Martin R. S. McCoustra e David Field. "Spontaneous polarization of solid CO on water ices and some astrophysical implications". Physical Chemistry Chemical Physics 18, n. 7 (2016): 5159–71. http://dx.doi.org/10.1039/c5cp07049j.

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Abstract (sommario):

Reflection absorption infrared spectroscopy (RAIRS) is used to show that when 20 monolayer (ML) films of solid CO are laid down on solid water substrates at 20 to 24 K, the films polarize spontaneously.

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43

Gudipati, Murthy S., e Louis J. Allamandola. "Facile Generation and Storage of Polycyclic Aromatic Hydrocarbon Ions in Astrophysical Ices". Astrophysical Journal 596, n. 2 (22 settembre 2003): L195—L198. http://dx.doi.org/10.1086/379595.

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44

Sandford, S. A., L. J. Allamandola, A. G. G. M. Tielens e G. J. Valero. "Laboratory studies of the infrared spectral propertries of CO in astrophysical ices". Astrophysical Journal 329 (giugno 1988): 498. http://dx.doi.org/10.1086/166395.

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45

de Barros, A. L. F., A. Bergantini, A. Domaracka, H. Rothard, P. Boduch e E. F. da Silveira. "Radiolysis of NH3:CO ice mixtures – implications for Solar system and interstellar ices". Monthly Notices of the Royal Astronomical Society 499, n. 2 (19 settembre 2020): 2162–72. http://dx.doi.org/10.1093/mnras/staa2865.

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Abstract (sommario):

ABSTRACT Experimental results on the processing of NH3:CO ice mixtures of astrophysical relevance by energetic (538 MeV 64Ni24+) projectiles are presented. NH3 and CO are two molecules relatively common in interstellar medium and Solar system; they may be precursors of amino acids. 64Ni ions may be considered as representative of heavy cosmic ray analogues. Laboratory data were collected using mid-infrared Fourier transform spectroscopy and revealed the formation of ammonium cation (NH$_4^+$), cyanate (OCN−), molecular nitrogen (N2), and CO2. Tentative assignments of carbamic acid (NH2COOH), formate ion (HCOO−), zwitterionic glycine (NH$_3^+$CH2COO−), and ammonium carbamate (NH$_4^+$NH2COO−) are proposed. Despite the confirmation on the synthesis of several complex species bearing C, H, O, and N atoms, no N–O-bearing species was detected. Moreover, parameters relevant for computational astrophysics, such as destruction and formation cross-sections, are determined for the precursor and the main detected species. Those values scale with the electronic stopping power (Se) roughly as σ ∼ a S$_\mathrm{ e}^n$, where n ∼ 3/2. The power law is helpful for predicting the CO and NH3 dissociation and CO2 formation cross-sections for other ions and energies; these predictions allow estimating the effects of the entire cosmic ray radiation field.

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46

Vasconcelos, F. A., S. Pilling, W. R. M. Rocha, H. Rothard e P. Boduch. "Radiolysis of N2-rich astrophysical ice by swift oxygen ions: implication for space weathering of outer solar system bodies". Physical Chemistry Chemical Physics 19, n. 35 (2017): 24154–65. http://dx.doi.org/10.1039/c7cp04408a.

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47

Woon, D. "Ab Initio Quantum Chemical Studies of Reactions in Astrophysical Ices 1. Aminolysis, Hydrolysis, and Polymerization in H2CO/NH3/H2O Ices". Icarus 142, n. 2 (dicembre 1999): 550–56. http://dx.doi.org/10.1006/icar.1999.6227.

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48

Collings, M. P., J. W. Dever, M. R. S. McCoustra e H. J. Fraser. "Implications of Ice Morphology for Comet Formation". Highlights of Astronomy 13 (2005): 491–94. http://dx.doi.org/10.1017/s1539299600016397.

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Abstract (sommario):

AbstractLaboratory surface science under ultra-high vacuum (UHV) conditions allows us to simulate the growth of ices in astrophysical environments. Using the techniques of temperature programmed desorption (TPD), reflection-absorption infrared spectroscopy (RAIRS) and micro-balance methods, we have studied binary ice systems consisting of water (H2O) and variety of other species including carbon monoxide (CO), at astrophysically relevant conditions of temperature and pressure. We present results that demonstrate that the morphology of water ice has an important influence on the behavior of such systems, by allowing processes such as diffusion and trapping that can not be understood through a knowledge of the binding energies of the species alone. Through an understanding of the implications of water ice morphology on the behavior of ice mixtures in the interstellar environment, additional constraints can be placed on the thermodynamic conditions and ice compositions during comet formation.

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49

Nuevo, Michel, Christopher K. Materese e Scott A. Sandford. "THE PHOTOCHEMISTRY OF PYRIMIDINE IN REALISTIC ASTROPHYSICAL ICES AND THE PRODUCTION OF NUCLEOBASES". Astrophysical Journal 793, n. 2 (15 settembre 2014): 125. http://dx.doi.org/10.1088/0004-637x/793/2/125.

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50

Quirico, Eric, Bernard Schmitt, Roberto Bini e Pier Remigio Salvi. "Spectroscopy of some ices of astrophysical interest: SO2, N2 and N2: CH4 mixtures". Planetary and Space Science 44, n. 9 (settembre 1996): 973–86. http://dx.doi.org/10.1016/0032-0633(96)00006-2.

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