150 results on '"Ioppolo, S."'
Search Results
2. Spectroscopic sizing of interstellar icy grains with JWST
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Dartois, E., Noble, J. A., Caselli, P., Fraser, H. J., Jiménez-Serra, I., Maté, B., McClure, M. K., Melnick, G. J., Pendleton, Y. J., Shimonishi, T., Smith, Z. L., Sturm, J. A., Taillard, A., Wakelam, V., Boogert, A. C. A., Drozdovskaya, M. N., Erkal, J., Harsono, D., Herrero, V. J., Ioppolo, S., Linnartz, H., McGuire, B. A., Perotti, G., Qasim, D., and Rocha, W. R. M. more...
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- 2024
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Catalog
3. An Ice Age JWST inventory of dense molecular cloud ices
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McClure, M. K., Rocha, W. R. M., Pontoppidan, K. M., Crouzet, N., Chu, L. E. U., Dartois, E., Lamberts, T., Noble, J. A., Pendleton, Y. J., Perotti, G., Qasim, D., Rachid, M. G., Smith, Z. L., Sun, Fengwu, Beck, Tracy L., Boogert, A. C. A., Brown, W. A., Caselli, P., Charnley, S. B., Cuppen, Herma M., Dickinson, H., Drozdovskaya, M. N., Egami, E., Erkal, J., Fraser, H., Garrod, R. T., Harsono, D., Ioppolo, S., Jiménez-Serra, I., Jin, M., Jørgensen, J. K., Kristensen, L. E., Lis, D. C., McCoustra, M. R. S., McGuire, Brett A., Melnick, G. J., Öberg, Karin I., Palumbo, M. E., Shimonishi, T., Sturm, J. A., van Dishoeck, E. F., and Linnartz, H. more...
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- 2023
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4. On the origin of molecular oxygen on the surface of Ganymede
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Migliorini, A., Kanuchova, Z., Ioppolo, S., Barbieri, M., Jones, N.C., Hoffmann, S.V., Strazzulla, G., Tosi, F., and Piccioni, G.
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- 2022
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5. The effect of dilution on the energy dissipation in water interstellar ice analogues: Probed by infrared irradiation.
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Schrauwen, J. G. M., Cuppen, H. M., Ioppolo, S., and Redlich, B.
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FREE electron lasers ,STRUCTURAL health monitoring ,ENERGY dissipation ,AMORPHOUS substances ,ASTROCHEMISTRY - Abstract
Context. Interstellar ices and their energetic processing play an important role in advancing the chemical complexity in space. Interstellar ices covering dust grains are intrinsically mixed, and it is assumed that physicochemical changes induced by energetic processing – triggered by photons, electrons, and ions – strongly depend on the content of the ice. Yet, the modelling of these complex mixed systems in experiments and theory is complicated. Aims. In this paper, we investigate the effect of infrared irradiation on a series of different molecules mixed with porous amorphous solid water (pASW) to study the release of vibrational energy in the hydrogen-bonding network of water as a function of mixing ratio and ice content. Particularly, we select mixtures of 20:1 H
2 O:X and 5:1 H2 O:X with X=CO2 , NH3 , or CH4 . Methods. Infrared radiation was supplied by the intense and tunable free electron laser (FEL) 2 at the HFML-FELIX facility. We monitored the structural changes in the interstellar ice analogue after resonant infrared excitation using Fourier-transform reflection absorption infrared (FT-RAIR) spectroscopy. Results. We observed that on-resonance irradiation at the OH-stretching vibration of pASW results in quantitatively identical changes compared to pure pASW for all investigated mixtures. The structural changes we observed closely resemble the previously reported local reordering. The 5:1 mixtures show weaker changes compared to pure pASW, with a decrease in strength from NH3 to CO2 . Conclusions. Since the hydrogen-bonding network of pASW restructures similarly upon FEL irradiation, regardless of the mixing component, treating ice layers in models that simulate energy dissipation in the hydrogen-bonding network as pure H2O ice layers can be a justified approximation. Hence, complex systems might not always be necessary to describe the infrared energetic processing of ices. [ABSTRACT FROM AUTHOR] more...- Published
- 2024
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6. Mid-IR and VUV spectroscopic characterisation of thermally processed and electron irradiated CO2 astrophysical ice analogues
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Mifsud, D.V., Kaňuchová, Z., Ioppolo, S., Herczku, P., Traspas Muiña, A., Field, T.A., Hailey, P.A., Juhász, Z., Kovács, S.T.S., Mason, N.J., McCullough, R.W., Pavithraa, S., Rahul, K.K., Paripás, B., Sulik, B., Chou, S.-L., Lo, J.-I., Das, A., Cheng, B.-M., Rajasekhar, B.N., Bhardwaj, A., and Sivaraman, B. more...
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- 2022
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7. AQUILA: A laboratory facility for the irradiation of astrochemical ice analogs by keV ions.
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Rácz, R., Kovács, S. T. S., Lakatos, G., Rahul, K. K., Mifsud, D. V., Herczku, P., Sulik, B., Juhász, Z., Perduk, Z., Ioppolo, S., Mason, N. J., Field, T. A., Biri, S., and McCullough, R. W.
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GALACTIC cosmic rays ,INTERSTELLAR molecules ,INTERSTELLAR medium ,DUST ,SOLAR system ,ASTROCHEMISTRY - Abstract
The detection of various molecular species, including complex organic molecules relevant to biochemical and geochemical processes, in astronomical settings, such as the interstellar medium or the outer solar system, has led to the increased need for a better understanding of the chemistry occurring in these cold regions of space. In this context, the chemistry of ices prepared and processed at cryogenic temperatures has proven to be of particular interest due to the fact that many interstellar molecules are believed to originate within the icy mantles adsorbed on nano- and micro-scale dust particles. The chemistry leading to the formation of such molecules may be initiated by ionizing radiation in the form of galactic cosmic rays or stellar winds, and thus, there has been an increased interest in commissioning experimental setups capable of simulating and better characterizing this solid-phase radiation astrochemistry. In this article, we describe a new facility called AQUILA (Atomki-Queen's University Ice Laboratory for Astrochemistry), which has been purposefully designed to study the chemical evolution of ices analogous to those that may be found in the dense interstellar medium or the outer solar system as a result of their exposure to keV ion beams. The results of some ion irradiation studies of CH
3 OH ice at 20 K are discussed to exemplify the experimental capabilities of the AQUILA as well as to highlight its complementary nature to another laboratory astrochemistry setup at our institute. [ABSTRACT FROM AUTHOR] more...- Published
- 2024
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8. Laboratory and Computational Studies of Interstellar Ices.
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Cuppen, Herma M., Linnartz, H., and Ioppolo, S.
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Ice mantles play a crucial role in shaping the astrochemical inventory of molecules during star and planet formation. Small-scale molecular processes have a profound impact on large-scale astronomical evolution. The areas of solid-state laboratory astrophysics and computational chemistry involve the study of these processes. We review laboratory efforts in ice spectroscopy, methodological advances and challenges, and laboratory and computational studies of ice physics and ice chemistry. We place the last of these in context with ice evolution from clouds to disks. Three takeaway messages from this review are: Laboratory and computational studies allow interpretation of astronomical ice spectra in terms of identification, ice morphology, and local environmental conditions as well as the formation of the involved chemical compounds. A detailed understanding of the underlying processes is needed to build reliable astrochemical models to make predictions about abundances in space. The relative importance of the different ice processes studied in the laboratory and computationally changes during the process of star and planet formation. [ABSTRACT FROM AUTHOR] more...
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- 2024
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9. A non-energetic mechanism for glycine formation in the interstellar medium
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Ioppolo, S., Fedoseev, G., Chuang, K.-J., Cuppen, H. M., Clements, A. R., Jin, M., Garrod, R. T., Qasim, D., Kofman, V., van Dishoeck, E. F., and Linnartz, H.
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- 2021
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10. An experimental study of the surface formation of methane in interstellar molecular clouds
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Qasim, D., Fedoseev, G., Chuang, K.-J., He, J., Ioppolo, S., van Dishoeck, E. F., and Linnartz, H.
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- 2020
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11. Grain Surface Models and Data for Astrochemistry
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Cuppen, H. M., Walsh, C., Lamberts, T., Semenov, D., Garrod, R. T., Penteado, E. M., and Ioppolo, S.
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- 2017
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12. The edge-on protoplanetary disk HH 48 NE: II. Modeling ices and silicates.
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Sturm, J. A., McClure, M. K., Bergner, J. B., Harsono, D., Dartois, E., Drozdovskaya, M. N., Ioppolo, S., Öberg, K. I., Law, C. J., Palumbo, M. E., Pendleton, Y. J., Rocha, W. R. M., Terada, H., and Urso, R. G. more...
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PARTICLE size distribution ,PROTOPLANETARY disks ,GLACIAL Epoch ,CIRCUMSTELLAR matter ,SPACE telescopes ,RADIATIVE transfer - Abstract
Context. The abundance and distribution of ice in protoplanetary disks is critical for an understanding of the link between the composition of circumstellar matter and the composition of exoplanets. Edge-on protoplanetary disks are a useful tool for constraining this ice composition and its location in the disk because the spectral signatures of the ice can be observed in absorption against the continuum emission that arises from the warmer regions in the central disk. Aims. The aim of this work is to model ice absorption features in protoplanetary disks and to determine how well the abundance of the main ice species throughout the disk can be determined within the uncertainty of the physical parameter space. The edge-on proto-planetary disk around HH 48 NE, a target of the James Webb Space Telescope Early Release program Ice Age, is used as a reference system. Methods. We used the full anisotropic scattering capabilities of the radiative transfer code RADMC-3D to ray-trace the mid-infrared continuum. Using a constant parameterized ice abundance, we added ice opacities to the dust opacity in regions in which the disk was cold enough for the main carbon, oxygen, and nitrogen carriers to freeze out. Results. The global abundance relative to the dust content of the main ice carriers in HH 48 NE can be determined within a factor of 3 when the uncertainty of the physical parameters is taken into account. Ice features in protoplanetary disks can be saturated at an optical depth of ≲1 due to local saturation. Ices are observed at various heights in the disk model, but in this model, spatial information is lost for features at wavelengths >7 µm when observing with James Webb Space Telescope because the angular resolution decreases towards longer wavelengths. Spatially observed ice optical depths cannot be directly related to column densities, as would be the case for direct absorption against a bright continuum source, because of radiative transfer effects. Vertical snowlines will not be a clear transition because the height of the snow surface increases radially, but their location may be constrained from observations using radiative transfer modeling. Radial snowlines are not really accessible. Not only the ice abundance, but also the inclination, the settling, the grain size distribution, and the disk mass have a strong impact on the observed ice absorption features in disks. Relative changes in the ice abundance can only be inferred from observations if the source structure is well constrained. [ABSTRACT FROM AUTHOR] more...
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- 2023
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13. The edge-on protoplanetary disk HH 48 NE: I. Modeling the geometry and stellar parameters.
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Sturm, J. A., McClure, M. K., Law, C. J., Harsono, D., Bergner, J. B., Dartois, E., Drozdovskaya, M. N., Ioppolo, S., Öberg, K. I., Palumbo, M. E., Pendleton, Y. J., Rocha, W. R. M., Terada, H., and Urso, R. G. more...
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PROTOPLANETARY disks ,GEOMETRIC modeling ,SPECTRAL energy distribution ,RADIATIVE transfer ,ATMOSPHERIC layers ,GLACIAL Epoch - Abstract
Context. Observations of edge-on disks are an important tool for constraining general protoplanetary disk properties that cannot be determined in any other way. However, most radiative transfer models cannot simultaneously reproduce the spectral energy distributions (SEDs) and resolved scattered light and submillimeter observations of these systems because the geometry and dust properties are different at different wavelengths. Aims. We simultaneously constrain the geometry of the edge-on protoplanetary disk HH 48 NE and the characteristics of the host star. HH 48 NE is part of the JWST early-release science program Ice Age. This work serves as a stepping stone toward a better understanding of the physical structure of the disk and of the icy chemistry in this particular source. This type of modeling lays the groundwork for studying other edge-on sources that are to be observed with the JWST. Methods. We fit a parameterized dust model to HH 48 NE by coupling the radiative transfer code RADMC-3D and a Markov chain Monte Carlo framework. The dust structure was fit independently to a compiled SED, a scattered light image at 0.8 µm, and an ALMA dust continuum observation at 890 µm. Results. We find that 90% of the dust mass in HH 48 NE is settled to the disk midplane. This is less than in average disks. The atmospheric layers of the disk also exclusively contain large grains (0.3–10 µm). The exclusion of small grains in the upper atmosphere likely has important consequences for the chemistry because high-energy photons can penetrate very deeply. The addition of a relatively large cavity (~50 au in radius) is necessary to explain the strong mid-infrared emission and to fit the scattered light and continuum observations simultaneously. [ABSTRACT FROM AUTHOR] more...
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- 2023
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14. Sulfur Ion Implantations Into Condensed CO2: Implications for Europa.
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Mifsud, D. V., Kaňuchová, Z., Herczku, P., Juhász, Z., Kovács, S. T. S., Lakatos, G., Rahul, K. K., Rácz, R., Sulik, B., Biri, S., Rajta, I., Vajda, I., Ioppolo, S., McCullough, R. W., and Mason, N. J. more...
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ION implantation ,SULFUR ,RADIATION chemistry ,SURFACE chemistry ,SULFUR dioxide ,CHEMICAL processes - Abstract
The ubiquity of sulfur ions within the Jovian magnetosphere has led to suggestions that the implantation of these ions into the surface of Europa may lead to the formation of SO2. However, previous studies on the implantation of sulfur ions into H2O ice (the dominant species on the Europan surface) have failed to detect SO2 formation. Other studies concerned with similar implantations into CO2 ice, which is also known to exist on Europa, have offered seemingly conflicting results. In this letter, we describe the results of a study on the implantation of 290 keV S+ ions into condensed CO2 at 20 and 70 K. Our results demonstrate that SO2 is observed after implantation at 20 K, but not at the Europa‐relevant temperature of 70 K. We conclude that this process is likely not a reasonable mechanism for SO2 formation on Europa, and that other mechanisms should be explored instead. Plain Language Summary: SO2 ice is known to exist at the surface of one of Jupiter's moons; Europa. However, the method by which this ice forms is still uncertain. Due to the orbit of Europa being within the giant magnetosphere of Jupiter, it has been proposed that sulfur ions within the magnetosphere could implant into the cold surface ices on Europa and subsequently react to form SO2. However, laboratory experiments looking into the implantation of such ions into H2O ice (the dominant ice on Europa's surface) and CO2 ice have either failed to yield SO2 or have provided inconclusive results. We have therefore performed an experiment in which we have implanted high‐energy sulfur ions into CO2 ice at two temperatures. Our results indicate that such implantations are unlikely to be the mechanism by which the SO2 on Europa is formed, and that other chemical processes should be considered instead. Key Points: Sulfur ions were implanted into CO2 ices at 20 and 70 K to simulate Jovian magnetospheric radiation chemistry at the surface of EuropaSO2 was observed to be among the radiolytic products at 20 K, but not at the more Europa‐relevant temperature of 70 KAlternative explanations for the formation of SO2 on the surface of Europa should be considered [ABSTRACT FROM AUTHOR] more...
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- 2022
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15. Complementary and Emerging Techniques for Astrophysical Ices Processed in the Laboratory
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Allodi, M. A., Baragiola, R. A., Baratta, G. A., Barucci, M. A., Blake, G. A., Boduch, P., Brucato, J. R., Contreras, C., Cuylle, S. H., Fulvio, D., Gudipati, M. S., Ioppolo, S., Kaňuchová, Z., Lignell, A., Linnartz, H., Palumbo, M. E., Raut, U., Rothard, H., Salama, F., Savchenko, E. V., Sciamma-O’Brien, E., and Strazzulla, G. more...
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- 2013
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16. Surface formation routes of interstellar molecules: hydrogenation reactions in simple ices
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Ioppolo, S., Cuppen, H. M., and Linnartz, H.
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- 2011
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17. TeraHertz desorption emission spectroscopy (THz DES) of space relevant ices.
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Auriacombe, Olivier, Rea, S, Ioppolo, S, Oldfield, M, Parkes, S, Ellison, B, and Fraser, H J
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EMISSION spectroscopy ,ASTROCHEMISTRY ,MOLECULAR spectroscopy ,MASS spectrometry ,DESORPTION ,SEMICONDUCTOR lasers ,INTERSTELLAR medium ,TERAHERTZ materials - Abstract
We present an experimental instrument that performs laboratory-based gas-phase Terahertz Desorption Emission Spectroscopy (THz-DES) experiments in support of astrochemistry. The measurement system combines a terahertz heterodyne radiometer that uses room temperature semiconductor mixer diode technology previously developed for the purposes of Earth observation, with a high-vacuum desorption gas cell and high-speed digital sampling circuitry to enable high spectral and temporal resolution spectroscopy of molecular species with thermal discrimination. During use, molecules are condensed on to a liquid nitrogen cooled metal finger to emulate ice structures that may be present in space. Following deposition, thermal desorption is controlled and initiated by means of a heater and monitored via a temperature sensor. The 'rest frequency' spectral signatures of molecules released into the vacuum cell environment are detected by the heterodyne radiometer in real-time and characterized with high spectral resolution. To demonstrate the viability of the instrument, we have studied Nitrous Oxide (N
2 O). This molecule strongly emits within the terahertz (sub-millimetre wavelength) range and provide a suitable test gas and we compare the results obtained with more traditional techniques such as quadrupole mass spectrometry. The results obtained allow us to fully characterize the measurement method and we discuss its potential use as a laboratory tool in support of astrochemical observations of molecular species in the interstellar medium and the Solar System. [ABSTRACT FROM AUTHOR] more...- Published
- 2022
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18. Investigations on ancient mortars from the Basilian monastery of Fragalà
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Cardiano, Paola, Sergi, S., De Stefano, Concetta, Ioppolo, S., and Piraino, P.
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- 2008
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19. Long-term serological evaluation of patients with cystic echinococcosis treated with benzimidazole carbamates
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RIGANÒ, R., IOPPOLO, S., ORTONA, E., MARGUTTI, P., PROFUMO, E., ALI, M. D, VICO, B. DI, TEGGI, A., and SIRACUSANO, A.
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- 2002
20. Serum cytokine detection in the clinical follow up of patients with cystic echinococcosis
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RIGANÒ, R., PROFUMO, E., IOPPOLO, S., NOTARGIACOMO, S., TEGGI, A., and SIRACUSANO, A.
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- 1999
21. Vacuum ultraviolet photoabsorption spectroscopy of space-related ices: formation and destruction of solid carbonic acid upon 1 keV electron irradiation.
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Ioppolo, S., Kaňuchová, Z., James, R. L., Dawes, A., Ryabov, A., Dezalay, J., Jones, N. C., Hoffmann, S. V., Mason, N. J., and Strazzulla, G.
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VACUUM ultraviolet spectroscopy , *ASTROCHEMISTRY , *CARBONIC acid , *CARBONATES , *ENCELADUS (Satellite) , *INTERPLANETARY dust , *POLYMORPHISM (Crystallography) , *COSMIC rays - Abstract
Context. Carbonic acid (H2CO3) is a weak acid relevant to astrobiology which, to date, remains undetected in space. Experimental work has shown that the β-polymorph of H2CO3 forms under space relevant conditions through energetic (UV photon, electron, and cosmic ray) processing of CO2- and H2O-rich ices. Although its α-polymorph ice has been recently reassigned to the monomethyl ester of carbonic acid, a different form of H2CO3 ice may exist and is synthesized without irradiation through surface reactions involving CO molecules and OH radicals, that is to say γ-H2CO3. Aims. We aim to provide a systematic set of vacuum ultraviolet (VUV) photoabsorption spectroscopic data of pure carbonic acid that formed and was destroyed under conditions relevant to space in support of its future identification on the surface of icy objects in the Solar System by the upcoming Jupiter ICy moons Explorer mission and on interstellar dust by the James Webb Space Telescope spacecraft. Methods. We present VUV photoabsorption spectra of pure and mixed CO2 and H2O ices exposed to 1 keV electrons at 20 and 80 K to simulate different interstellar and Solar System environments. Ices were then annealed to obtain a layer of pure H2CO3 which was further exposed to 1 keV electrons at 20 and 80 K to monitor its destruction pathway. Fourier-transform infrared (FT-IR) spectroscopy was used as a secondary probe providing complementary information on the physicochemical changes within an ice. Results. Our laboratory work shows that the formation of solid H2CO3, CO, and O3 upon the energetic processing of CO2:H2O ice mixtures is temperature-dependent in the range between 20 and 80 K. The amorphous to crystalline phase transition of H2CO3 ice is investigated for the first time in the VUV spectral range by annealing the ice at 200 and 225 K. We have detected two photoabsorption bands at 139 and 200 nm, and we assigned them to β-H2CO3 and γ-H2CO3, respectively. We present VUV spectra of the electron irradiation of annealed H2CO3 ice at different temperatures leading to its decomposition into CO2, H2O, and CO ice. Laboratory results are compared to Cassini UltraViolet Imaging Spectrograph observations of the 70−90 K ice surface of Saturn's satellites Enceladus, Dione, and Rhea. [ABSTRACT FROM AUTHOR] more...
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- 2021
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22. A cryogenic ice setup to simulate carbon atom reactions in interstellar ices.
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Qasim, D., Witlox, M. J. A., Fedoseev, G., Chuang, K.-J., Banu, T., Krasnokutski, S. A., Ioppolo, S., Kästner, J., van Dishoeck, E. F., and Linnartz, H.
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ULTRAHIGH vacuum ,ICE clouds ,MOLECULAR clouds ,ATOMS ,ATOMIC beams ,ICE ,ICE nuclei - Abstract
The design, implementation, and performance of a customized carbon atom beam source for the purpose of investigating solid-state reaction routes in interstellar ices in molecular clouds are discussed. The source is integrated into an existing ultrahigh vacuum setup, SURFace REaction SImulation DEvice (SURFRESIDE
2 ), which extends this double atom (H/D, O, and N) beamline apparatus with a third atom (C) beamline to a unique system that is fully suited to explore complex organic molecule solid-state formation under representative interstellar cloud conditions. The parameter space for this system is discussed, which includes the flux of the carbon atoms hitting the ice sample, their temperature, and the potential impact of temperature on ice reactions. Much effort has been put into constraining the beam size to within the limits of the sample size with the aim of reducing carbon pollution inside the setup. How the C-atom beam performs is quantitatively studied through the example experiment, C +18 O2 , and supported by computationally derived activation barriers. The potential for this source to study the solid-state formation of interstellar complex organic molecules through C-atom reactions is discussed. [ABSTRACT FROM AUTHOR] more...- Published
- 2020
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23. Formation of complex molecules in translucent clouds: acetaldehyde, vinyl alcohol, ketene, and ethanol via "nonenergetic" processing of C2H2 ice.
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Chuang, K.-J., Fedoseev, G., Qasim, D., Ioppolo, S., Jäger, C., Henning, Th., Palumbo, M. E., van Dishoeck, E. F., and Linnartz, H.
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CHEMICAL processes ,ACETALDEHYDE ,SURFACE chemistry ,ETHANES ,ETHANOL ,ADDITION reactions ,INFRARED absorption - Abstract
Context. Complex organic molecules (COMs) have been identified toward high- and low-mass protostars as well as molecular clouds, suggesting that these interstellar species originate from the early stage(s) of starformation. The reaction pathways resulting in COMs described by the formula C2HnO, such as acetaldehyde (CH3CHO), vinyl alcohol (CH2CHOH), ketene (CH2CO), and ethanol (CH3CH2OH), are still under debate. Several of these species have been detected in both translucent and dense clouds, where chemical processes are dominated by (ground-state) atom and radical surface reactions. Therefore, efficient formation pathways are needed to account for their appearance well before the so-called catastrophic CO freeze-out stage starts. Aims. In this work, we investigate the laboratory possible solid-state reactions that involve simple hydrocarbons and OH-radicals along with H2O ice under translucent cloud conditions (1 ≤ AV ≤ 5 and nH ~ 103 cm-3). We focus on the interactions of C2H2 with H-atoms and OH-radicals, which are produced along the H2O formation sequence on grain surfaces at 10 K. Methods. Ultra-high vacuum experiments were performed to study the surface chemistry observed during C2H2 + O2 + H codeposition, where O2 was used for the in situ generation of OH-radicals. These C2H2 experiments were extended by a set of similar experiments involving acetaldehyde (CH3CHO) - an abundant product of C2H2 + O2 + H codeposition. Reflection absorption infrared spectroscopy was applied to in situ monitor the initial and newly formed species. After that, a temperature-programmed desorption experiment combined with a quadrupole mass spectrometer was used as a complementary analytical tool. The IR and QMS spectral assignments were further confirmed in isotope labeling experiments using 18O2. Results. The investigated 10 K surface chemistry of C2H2 with H-atoms and OH-radicals not only results in semi and fully saturated hydrocarbons, such as ethylene (C2H4) and ethane (C2H6), but it also leads to the formation of COMs, such as vinyl alcohol, acetaldehyde, ketene, ethanol, and possibly acetic acid. It is concluded that OH-radical addition reactions to C2H2, acting as a molecular backbone, followed by isomerization (i.e., keto-enol tautomerization) via an intermolecular pathway and successive hydrogenation provides so far an experimentally unreported solid-state route for the formation of these species without the need of energetic input. The kinetics of acetaldehyde reacting with impacting H-atoms leading to ketene and ethanol is found to have a preference for the saturated product. The astronomical relevance of the reaction network introduced here is discussed. [ABSTRACT FROM AUTHOR] more...
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- 2020
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24. Efficient surface formation route of interstellar hydroxylamine through NO hydrogenation. II. The multilayer regime in interstellar relevant ices.
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Fedoseev, G., Ioppolo, S., Lamberts, T., Zhen, J. F., Cuppen, H. M., and Linnartz, H.
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HYDROXYLAMINE , *SURFACES (Technology) , *NITROGEN oxides , *HYDROGENATION , *INTERSTELLAR medium , *COMPLEX compounds , *NITRIC oxide , *PHOTOLYSIS (Chemistry) - Abstract
Hydroxylamine (NH2OH) is one of the potential precursors of complex pre-biotic species in space. Here, we present a detailed experimental study of hydroxylamine formation through nitric oxide (NO) surface hydrogenation for astronomically relevant conditions. The aim of this work is to investigate hydroxylamine formation efficiencies in polar (water-rich) and non-polar (carbon monoxide-rich) interstellar ice analogues. A complex reaction network involving both final (N2O, NH2OH) and intermediate (HNO, NH2O·, etc.) products is discussed. The main conclusion is that hydroxyl-amine formation takes place via a fast and barrierless mechanism and it is found to be even more abundantly formed in a water-rich environment at lower temperatures. In parallel, we experimentally verify the non-formation of hydroxylamine upon UV photolysis of NO ice at cryogenic temperatures as well as the non-detection of NC- and NCO-bond bearing species after UV processing of NO in carbon monoxide-rich ices. Our results are implemented into an astrochemical reaction model, which shows that NH2OH is abundant in the solid phase under dark molecular cloud conditions. Once NH2OH desorbs from the ice grains, it becomes available to form more complex species (e.g., glycine and β-alanine) in gas phase reaction schemes. [ABSTRACT FROM AUTHOR] more...
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- 2012
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25. Water formation by surface O3 hydrogenation.
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Romanzin, C., Ioppolo, S., Cuppen, H. M., van Dishoeck, E. F., and Linnartz, H.
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WATER , *COSMIC abundances , *HYDROGENATION , *OZONE , *CHEMICAL kinetics , *SPECTRUM analysis , *MOLECULAR clouds , *ASTROPHYSICS - Abstract
Three solid state formation routes have been proposed in the past to explain the observed abundance of water in space: the hydrogenation reaction channels of atomic oxygen (O + H), molecular oxygen (O2 + H), and ozone (O3 + H). New data are presented here for the third scheme with a focus on the reactions O3 + H, OH + H and OH + H2, which were difficult to quantify in previous studies. A comprehensive set of H/D-atom addition experiments is presented for astronomically relevant temperatures. Starting from the hydrogenation/deuteration of solid O3 ice, we find experimental evidence for H2O/D2O (and H2O2/D2O2) ice formation using reflection absorption infrared spectroscopy. The temperature and H/D-atom flux dependence are studied and this provides information on the mobility of ozone within the ice and possible isotope effects in the reaction scheme. The experiments show that the O3 + H channel takes place through stages that interact with the O and O2 hydrogenation reaction schemes. It is also found that the reaction OH + H2 (OH + H), as an intermediate step, plays a prominent (less efficient) role. The main conclusion is that solid O3 hydrogenation offers a potential reaction channel for the formation of water in space. Moreover, the nondetection of solid ozone in dense molecular clouds is consistent with the astrophysical picture in which O3 + H is an efficient process under interstellar conditions. [ABSTRACT FROM AUTHOR] more...
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- 2011
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26. Formation of interstellar propanal and 1-propanol ice: a pathway involving solid-state CO hydrogenation.
- Author
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Qasim, D., Fedoseev, G., Chuang, K.-J., Taquet, V., Lamberts, T., He, J., Ioppolo, S., van Dishoeck, E. F., and Linnartz, H.
- Subjects
PROPIONALDEHYDE ,PROPANOLS ,HYDROGENATION ,INFRARED absorption ,INFRARED spectroscopy ,MASS spectrometry - Abstract
Context. 1-propanol (CH
3 CH2 CH2 OH) is a three carbon-bearing representative of the primary linear alcohols that may have its origin in the cold dark cores in interstellar space. To test this, we investigated in the laboratory whether 1-propanol ice can be formed along pathways possibly relevant to the prestellar core phase. Aims. We aim to show in a two-step approach that 1-propanol can be formed through reaction steps that are expected to take place during the heavy CO freeze-out stage by adding C2 H2 into the CO + H hydrogenation network via the formation of propanal (CH3 CH2 CHO) as an intermediate and its subsequent hydrogenation. Methods. Temperature programmed desorption-quadrupole mass spectrometry (TPD-QMS) was used to identify the newly formed propanal and 1-propanol. Reflection absorption infrared spectroscopy (RAIRS) was used as a complementary diagnostic tool. The mechanisms that can contribute to the formation of solid-state propanal and 1-propanol, as well as other organic compounds, during the heavy CO freeze-out stage are constrained by both laboratory experiments and theoretical calculations. Results. Here it is shown that recombination of HCO radicals formed upon CO hydrogenation with radicals formed via C2 H2 processing – H2 CCH and H3 CCH2 – offers possible reaction pathways to solid-state propanal and 1-propanol formation. This extends the already important role of the CO hydrogenation chain to the formation of larger complex organic molecules. The results are compared with ALMA observations. The resulting 1-propanol:propanal ratio concludes an upper limit of <0.35−0.55, which is complemented by computationally derived activation barriers in addition to the experimental results. [ABSTRACT FROM AUTHOR] more...- Published
- 2019
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27. Extension of the HCOOH and CO2 solid-state reaction network during the CO freeze-out stage: inclusion of H2CO.
- Author
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Qasim, D., Lamberts, T., He, J., Chuang, K.-J., Fedoseev, G., Ioppolo, S., Boogert, A. C. A., and Linnartz, H.
- Subjects
PHOSPHORS ,INFRARED absorption ,ICE cores ,INFRARED spectroscopy ,MASS spectrometry ,BRANCHING ratios - Abstract
Context. Formic acid (HCOOH) and carbon dioxide (CO
2 ) are simple species that have been detected in the interstellar medium. The solid-state formation pathways of these species under experimental conditions relevant to prestellar cores are primarily based off of weak infrared transitions of the HOCO complex and usually pertain to the H2 O-rich ice phase, and therefore more experimental data are desired. Aims. Here, we present a new and additional solid-state reaction pathway that can form HCOOH and CO2 ice at 10 K "non-energetically" in the laboratory under conditions related to the "heavy" CO freeze-out stage in dense interstellar clouds, i.e., by the hydrogenation of an H2 CO:O2 ice mixture. This pathway is used to piece together the HCOOH and CO2 formation routes when H2 CO or CO reacts with H and OH radicals. Methods. Temperature programmed desorption – quadrupole mass spectrometry (TPD-QMS) is used to confirm the formation and pathways of newly synthesized ice species as well as to provide information on relative molecular abundances. Reflection absorption infrared spectroscopy (RAIRS) is additionally employed to characterize reaction products and determine relative molecular abundances. Results. We find that for the conditions investigated in conjunction with theoretical results from the literature, H + HOCO and HCO + OH lead to the formation of HCOOH ice in our experiments. Which reaction is more dominant can be determined if the H + HOCO branching ratio is more constrained by computational simulations, as the HCOOH:CO2 abundance ratio is experimentally measured to be around 1.8:1. H + HOCO is more likely than OH + CO (without HOCO formation) to form CO2 . Isotope experiments presented here further validate that H + HOCO is the dominant route for HCOOH ice formation in a CO-rich CO:O2 ice mixture that is hydrogenated. These data will help in the search and positive identification of HCOOH ice in prestellar cores. [ABSTRACT FROM AUTHOR] more...- Published
- 2019
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28. Synthesis of solid-state complex organic molecules through accretion of simple species at low temperatures.
- Author
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Qasim, D., Fedoseev, G., Chuang, K.-J., Taquet, V., Lamberts, T., He, J., Ioppolo, S., van Dishoeck, E. F., Linnartz, H., Salama, Farid, and Linnartz, Harold
- Abstract
Complex organic molecules (COMs) have been detected in the gas-phase in cold and lightless molecular cores. Recent solid-state laboratory experiments have provided strong evidence that COMs can be formed on icy grains through 'non-energetic' processes. In this contribution, we show that propanal and 1-propanol can be formed in this way at the low temperature of 10 K. Propanal has already been detected in space. 1-propanol is an astrobiologically relevant molecule, as it is a primary alcohol, and has not been astronomically detected. Propanal is the major product formed in the C
2 H2 + CO + H experiment, and 1-propanol is detected in the subsequent propanal + H experiment. ALMA observations towards IRAS 16293-2422B are discussed and provide a 1-propanol:propanal upper limit of < 0.35–0.55, which are complemented by computationally-derived activation barriers in addition to the performed laboratory experiments. [ABSTRACT FROM AUTHOR] more...- Published
- 2019
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29. H2 chemistry in interstellar ices: the case of CO ice hydrogenation in UV irradiated CO:H2 ice mixtures.
- Author
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Chuang, K.-J., Fedoseev, G., Qasim, D., Ioppolo, S., van Dishoeck, E. F., and Linnartz, H.
- Subjects
INTERPLANETARY dust ,HYDROGENATION ,ICE ,CARBON monoxide ,ULTRAVIOLET radiation - Abstract
Context. In dense clouds, hydrogenation reactions on icy dust grains are key in the formation of molecules, like formaldehyde, methanol, and complex organic molecules (COMs). These species form through the sequential hydrogenation of CO ice. Although molecular hydrogen (H
2 ) abundances can be four orders of magnitude higher than those of free H-atoms in dense clouds, H2 surface chemistry has been largely ignored; several laboratory studies show that H2 does not actively participate in "non-energetic" ice chemistry because of the high activation energies required. Aims. For the example of CO ice hydrogenation, we experimentally investigated the potential role of H2 molecules on the surface chemistry when energetic processing (i.e., UV photolysis) is involved. We test whether additional hydrogenation pathways become available upon UV irradiation of a CO:H2 ice mixture and whether this reaction mechanism also applies to other chemical systems. Methods. Ultra-high vacuum (UHV) experiments were performed at 8–20 K. A pre-deposited solid mixture of CO:H2 was irradiated with UV-photons. Reflection absorption infrared spectroscopy (RAIRS) was used as an in situ diagnostic tool. Single reaction steps and possible isotopic effects were studied by comparing results from CO:H2 and CO:D2 ice mixtures. Results. After UV-irradiation of a CO:H2 ice mixture, two photon-induced products, HCO and H2 CO, are unambiguously detected. The proposed reaction mechanism involves electronically excited CO in the following reaction steps: CO + hν→CO* , CO* + H2 →HCO + H where newly formed H-atoms are then available for further hydrogenation reactions. The HCO formation yields have a strong temperature dependence for the investigated regime, which is most likely linked to the H2 sticking coefficient. Moreover, the derived formation cross section reflects a cumulative reaction rate that mainly determined by both the H-atom diffusion rate and initial concentration of H2 at 8–20 K and that is largely determined by the H2 sticking coefficient. Finally, the astronomical relevance of this photo-induced reaction channel is discussed. [ABSTRACT FROM AUTHOR] more...- Published
- 2018
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30. Production of complex organic molecules: H-atom addition versus UV irradiation.
- Author
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Chuang, K.-J., Fedoseev, G., Qasim, D., Ioppolo, S., van Dishoeck, E. F., and Linnartz, H.
- Subjects
HYDROGEN atom ,ULTRAVIOLET radiation ,SOLID state chemistry ,LIGHT absorption ,ASTROCHEMISTRY - Abstract
Complex organic molecules (COMs) have been identified in different environments in star-forming regions. Laboratory studies show that COMs form in the solid state, on icy grains, typically following a 'non-energetic' (atom-addition) or 'energetic' (UV-photon absorption) trigger. So far, such studies have been largely performed for single processes. Here, we present the first work that quantitatively investigates both the relative importance and the cumulative effect of '(non-)energetic' processing. We focus on astronomically relevant CO:CH
3 OH = 4:1 ice analogues exposed to doses relevant for the collapse stage of dense clouds. Hydrogenation experiments result in the formation of methyl formate (MF; HC(O)OCH3 ), glycolaldehyde (GA; HC(O)CH2 OH) and ethylene glycol (EG; H2 C(OH)CH2 OH) at 14 K. The absolute abundances and the abundance fractions are found to be dependent on the H-atom/CO:CH3 OH-molecule ratios and on the overall deposition rate. In the case that ices are exposed to UV photons only, several different COMs are found. Typically, the abundance fractions are 0.2 for MF, 0.3 for GA and 0.5 for EG as opposed to the values found in pure hydrogenation experiments without UV in which MF is largely absent: 0.0, 0.2-0.6 and 0.8-0.4, respectively. In experiments where both are applied, overall COM abundances drop to about half of those found in the pure UV irradiation experiments, but the composition fractions are very similar. This implies COM ratios can be used as a diagnostic tool to derive the processing history of an ice. Solid-state branching ratios derived here for GA and EG compare well with observations, while the MF case cannot be explained by solid-state conditions investigated here. [ABSTRACT FROM AUTHOR] more...- Published
- 2017
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31. Simultaneous hydrogenation and UV-photolysis experiments of NO in CO-rich interstellar ice analogues; linking HNCO, OCN-, NH2CHO, and NH2OH.
- Author
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Fedoseev, G., Chuang, K.-J., van Dishoeck, E. F., Ioppolo, S., and Linnartz, H.
- Subjects
HYDROGENATION ,ULTRAVIOLET photolysis ,MOLECULAR clouds ,NITROGEN oxides ,HYDROXYLAMINE - Abstract
The laboratory work presented here simulates the chemistry on icy dust grains as typical for the 'CO freeze-out stage' in dark molecular clouds. It differs from previous studies in that solid-state hydrogenation and vacuum UV photoprocessing are applied simultaneously to co-depositing molecules. In parallel, the reactions at play are described for fully characterized laboratory conditions. The focus is on the formation of molecules containing both carbon and nitrogen atoms, starting with NO in CO-, H
2 CO-, and CH3 OH-rich ices at 13 K. The experiments yield three important conclusions. (1) Without UV processing hydroxylamine (NH2 OH) is formed, as reported previously. (2)WithUVprocessing (energetic) NH2 is formed through photodissociation of NH2 OH. This radical is key in the formation of species with an N-C bond. (3) The formation of three N-C bearing species, HNCO, OCN-, and NH2 CHO, is observed. The experiments put a clear chemical link between these species; OCN- is found to be a direct derivative of HNCO and the latter is shown to have the same precursor as formamide (NH2 CHO). Moreover, the addition of VUV competing channels decreases the amount of NO molecules converted into NH2 OH by at least one order of magnitude. Consequently, this decrease in NH2OH formation yield directly influences the amount of NO molecules that can be converted into HNCO, OCN-, and NH2 CHO. [ABSTRACT FROM AUTHOR] more...- Published
- 2016
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32. H-atom addition and abstraction reactions in mixed CO, H2CO and CH3OH ices - an extended view on complex organic molecule formation.
- Author
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Chuang, K. J., Fedoseev, G., Ioppolo, S., van Dishoeck, E. F., and Linnartz, H.
- Subjects
HYDROGEN atom ,ABSTRACTION reactions ,ADDITION reactions ,CARBON monoxide ,ASTRONOMICAL observations ,PROTOSTARS ,CLOUDS - Abstract
Complex organic molecules (COMs) have been observed not only in the hot cores surrounding low- and high-mass protostars, but also in cold dark clouds. Therefore, it is interesting to understand how such species can be formed without the presence of embedded energy sources. We present new laboratory experiments on the low-temperature solid state formation of three complex molecules - methyl formate (HC(O)OCH
3 ), glycolaldehyde (HC(O)CH2 OH) and ethylene glycol (H2 C(OH)CH2 OH) - through recombination of free radicals formed via H-atom addition and abstraction reactions at different stages in the CO→H2 CO→CH3 OH hydrogenation network at 15 K. The experiments extend previous CO hydrogenation studies and aim at resembling the physical-chemical conditions typical of the CO freeze-out stage in dark molecular clouds, when H2 CO and CH3 OH form by recombination of accreting CO molecules and H-atoms on ice grains. We confirm that H2 CO, once formed through CO hydrogenation, not only yields CH3 OH through ongoing H-atom addition reactions, but is also subject to H-atom-induced abstraction reactions, yielding CO again. In a similar way, H2 CO is also formed in abstraction reactions involving CH3 OH. The dominant methanol H-atom abstraction product is expected to be CH2 OH, while H-atom additions to H2 CO should at least partially proceed through CH3 O intermediate radicals. The occurrence of H-atom abstraction reactions in ice mantles leads to more reactive intermediates (HCO, CH3 O and CH2 OH) than previously thought, when assuming sequential H-atom addition reactions only. This enhances the probability to form COMs through radical-radical recombination without the need of UV photolysis or cosmic rays as external triggers. [ABSTRACT FROM AUTHOR] more...- Published
- 2016
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33. Low-temperature chemistry between water and hydroxyl radicals: H/D isotopic effects.
- Author
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Lamberts, T., Fedoseev, G., Puletti, F., Ioppolo, S., Cuppen, H. M., and Linnartz, H.
- Subjects
HYDROXYL group ,MONTE Carlo method ,WATER ,ISOTOPES ,ASTRONOMY - Abstract
Sets of systematic laboratory experiments are presented - combining Ultra High Vacuum cryogenic and plasma-line deposition techniques - that allow us to compare H/D isotopic effects in the reaction of H
2 O (D2 O) ice with the hydroxyl radical OD (OH). The latter is known to play a key role as intermediate species in the solid-state formation of water on icy grains in space. The main finding of our work is that the reaction H2 O + OD → OH + HDO occurs and that this may affect the HDO/H2 O abundances in space. The opposite reaction D2 O + OH → OD + HDO is much less effective, and also given the lower D2 O abundances in space not expected to be of astronomical relevance. The experimental results are extended to the other four possible reactions between hydroxyl and water isotopes and are subsequently used as input for Kinetic Monte Carlo simulations. This way we interpret our findings in an astronomical context, qualitatively testing the influence of the reaction rates. [ABSTRACT FROM AUTHOR] more...- Published
- 2016
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34. Spectroscopic constraints on CH3OH formation: CO mixed with CH3OH ices towards young stellar objects.
- Author
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Penteado, E. M., Boogert, A. C. A., Pontoppidan, K. M., Ioppolo, S., Blake, G. A., and Cuppen, H. M.
- Subjects
ASTRONOMICAL spectroscopy ,METHYL groups ,CARBON monoxide ,INFRARED absorption ,HYDROGEN bonding - Abstract
The prominent infrared absorption band of solid CO - commonly observed towards young stellar objects (YSOs) - consists of three empirically determined components. The broad 'red component' (2136 cm<superscript>-1, 4.681 µm) is generally attributed to solid CO mixed in a hydrogen-bonded environment. Usually, CO embedded in the abundantly present water is considered. However, CO:H
2 O mixtures cannot reproduce the width and position of the observed red component without producing a shoulder at 2152 cm-1 , which is not observed in astronomical spectra. Cuppen et al. showed that CO:CH3 OH mixtures do not suffer from this problem. Here, this proposition is expanded by comparing literature laboratory spectra of different CO-containing ice mixtures to high-resolution (R = λ/Δλ = 25 000) spectra of the massive YSO AFGL 7009S and of the low-mass YSO L1489 IRS. The previously unpublished spectrum of AFGL 7009S shows a wide band of solid13 CO, the first detection of13 CO ice in the polar phase. In this source, both the12 CO and13 CO ice bands are well fitted with CO:CH3 OH mixtures, while respecting the profiles and depths of the methanol bands at other wavelengths, whereas mixtures with H2 O cannot. The presence of a gradient in the CO:CH3 OH mixing ratio in the grain mantles is also suggested. Towards L1489 IRS, the profile of the12 CO band is also better fitted with CH3 OH-containing ices, although the CH3 OH abundance needed is a factor of 2.4 above previous measurements. Overall, however, the results are reasonably consistent with models and experiments about formation of CH3 OH by the hydrogenation of CO ices. [ABSTRACT FROM AUTHOR] more...- Published
- 2015
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35. Thermal H/D exchange in polar ice - deuteron scrambling in space.
- Author
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Lamberts, T., Ioppolo, S., Cuppen, H. M., Fedoseev, G., and Linnartz, H.
- Subjects
- *
DEUTERON reactions , *ASTROCHEMISTRY , *SOLID state chemistry , *INTERSTELLAR medium , *ULTRAHIGH vacuum - Abstract
We have investigated the thermally induced proton/deuteron exchange in mixed amorphous H2O:D2O ices by monitoring the change in intensity of characteristic vibrational bending modes of H2O, HDO, and D2O with time and as function of temperature. The experiments have been performed using an ultrahigh vacuum setup equipped with an infrared spectrometer that is used to investigate the spectral evolution of homogeneously mixed ice upon co-deposition in thin films, for temperatures in the 90-140K domain. With this non-energetic detection method, we find a significantly lower activation energy for H/D exchange - 3840 ± 125K - than previously reported. Very likely this is due to the amorphous nature of the interstellar ice analogues involved. This provides reactive time-scales (τ < 104 yr at T > 70 K) fast enough for the process to be important in interstellar environments. Consequently, an astronomical detection of D2O will be even more challenging because of its potential to react with H2O to form HDO. Furthermore, additional experiments, along with previous studies, show that proton/deuteron swapping also occurs in ice mixtures of water with other hydrogen-bonded molecules, in particular on the OH and NH moieties. We conclude that H/D exchange in ices is a more general process that should be incorporated into ice models that are applied to protoplanetary discs or to simulate the warming up of cometary ices in their passage of the perihelion, to examine the extent of its influence on the final deuteron over hydrogen ratio. [ABSTRACT FROM AUTHOR] more...
- Published
- 2015
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36. Atom addition reactions in interstellar ice analogues.
- Author
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Linnartz, H., Ioppolo, S., and Fedoseev, G.
- Subjects
- *
CHEMICAL reactions , *INTERSTELLAR medium , *ASTRONOMICAL observations , *SPACE vehicles , *ICE , *MAGELLANIC clouds - Abstract
It was in ‘The Magellanic Cloud’ (1955) – a science fiction novel by Stanislaw Lem – that engineers travelling to another star noticed that their spacecraft for unknown reasons overheated. The cause had to be outside the spaceship, but obviously there was only emptiness, at least compared to terrestrial conditions. The space between the stars, the interstellar medium (ISM), however, is not completely empty and at the high speed of the spacecraft the cross-section with impacting particles, even from such a dilute environment, was found to be sufficient to cause an overheating. Today, 60 years later, the ISM has been studied in detail by astronomical observations, reproduced in dedicated laboratory experiments and simulated by complex astrochemical models. The space between the stars is, indeed, far from empty; it comprises gas, dust and ice and the molecules detected so far are both small (diatomics) and large (long carbon chains, PAHs and fullerenes), stable and reactive (radicals, ions, and excited molecules) evidencing an exotic and fascinating chemistry, taking place at low densities, low temperatures and experiencing intense radiation fields. Astrochemists explain the observed chemical complexity in space – so far 185 different molecules (not including isotopologues) have been identified – as the cumulative outcome of reactions in the gas phase and on icy dust grains. Gas phase models explain the observed abundances of a substantial part of the observed species, but fail to explain the number densities for stable molecules, as simple as water, methanol or acetonitrile – one of the most promising precursor species for the simplest amino acid glycine – as well as larger compounds such as glycolaldehyde, dimethylether and ethylene glycol. Evidence has been found that these and other complex species, including organic ones, form on icy dust grains that act as catalytic sites for molecule formation. It is here where particles ‘accrete, meet, and greet’ (i.e. freeze out, diffuse and react) upon energetic and non-energetic processing, such as irradiation by vacuum UV light, interaction with impacting particles (atoms, electrons and cosmic rays) or heating. This review paper summarises the state-of-the-art in laboratory based interstellar ice chemistry. The focus is on atom addition reactions, illustrating how water, carbon dioxide and methanol can form in the solid state at astronomically relevant temperatures, and also the formation of more complex species such as hydroxylamine, an important prebiotic molecule, and glycolaldehyde, the smallest sugar, is discussed. These reactions are particularly relevant during the ‘dark’ ages of star and planet formation, i.e. when the role of UV light is restricted. A quantitative characterization of such processes is only possible through dedicated laboratory studies, i.e. under full control of a large set of parameters such as temperature, atom-flux, and ice morphology. The resulting numbers, physical and chemical constants, e.g. barrier heights, reaction rates and branching ratios, provide information on the molecular processes at work and are needed as input for astrochemical models, in order to bridge the timescales typical for a laboratory setting to those needed to understand the evolutionary stages of the ISM. Details of the experiments as well as the astrochemical impact of the results are discussed. [ABSTRACT FROM PUBLISHER] more...
- Published
- 2015
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37. Experimental evidence for glycolaldehyde and ethylene glycol formation by surface hydrogenation of CO molecules under dense molecular cloud conditions.
- Author
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Fedoseev, G., Cuppen, H. M., Ioppolo, S., Lamberts, T., and Linnartz, H.
- Subjects
INTERSTELLAR medium ,GLYCOLALDEHYDE ,ETHYLENE glycol ,HYDROGENATION ,MOLECULAR clouds ,SOLID state chemistry - Abstract
This study focuses on the formation of two molecules of astrobiological importance -- glycolaldehyde (HC(O)CH
2 OH) and ethylene glycol (H2 C(OH)CHpt>2OH) -- by surface hydrogenation of CO molecules. Our experiments aim at simulating the CO freeze-out stage in interstellar dark cloud regions, well before thermal and energetic processing become dominant. It is shown that along with the formation of H 2 CO and CH3 OH -- two well-established products of CO hydrogenation -- also molecules with more than one carbon atom form. The key step in this process is believed to be the recombination of two HCO radicals followed by the formation of a C-C bond. The experimentally established reaction pathways are implemented into a continuous-time random-walk Monte Carlo model, previously used to model the formation of CH3 OH on astrochemical time-scales, to study their impact on the solid-state abundances in dense interstellar clouds of glycolaldehyde and ethylene glycol. [ABSTRACT FROM AUTHOR] more...- Published
- 2015
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38. Deuterium enrichment of ammonia produced by surface N+H/D addition reactions at low temperature.
- Author
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Fedoseev, G., Ioppolo, S., and Linnartz, H.
- Subjects
- *
AMMONIA analysis , *DEUTERIUM , *LOW temperatures , *CHEMICAL reactions , *ISOTOPOLOGUES , *ASTRONOMICAL observations - Abstract
The surface formation of NH3 and its deuterated isotopologues – NH2D, NHD2, and ND3 – is investigated at low temperatures through the simultaneous addition of hydrogen and deuterium atoms to nitrogen atoms in CO-rich interstellar ice analogues. The formation of all four ammonia isotopologues is only observed up to 15 K, and drops below the detection limit for higher temperatures. Differences between hydrogenation and deuteration yields result in a clear deviation from a statistical distribution in favour of deuterium enriched species. The data analysis suggests that this is due to a higher sticking probability of D atoms to the cold surface, a property that may generally apply to molecules that are formed in low temperature surface reactions. The results found here are used to interpret ammonia–deuterium fractionation as observed in pre-protostellar cores. [ABSTRACT FROM AUTHOR] more...
- Published
- 2015
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39. Low-temperature surface formation of NH3 and HNCO: hydrogenation of nitrogen atoms in CO-rich interstellar ice analogues.
- Author
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Fedoseev, G., Ioppolo, S., Zhao, D., Lamberts, T., and Linnartz, H.
- Subjects
- *
LOW temperatures , *AMMONIA analysis , *ISOCYANIC acid , *NITROGEN analysis , *HYDROGENATION , *CARBON monoxide , *INTERSTELLAR medium - Abstract
Solid-state astrochemical reaction pathways have the potential to link the formation of small nitrogen-bearing species, like NH3 and HNCO, and prebiotic molecules, specifically amino acids. To date, the chemical origin of such small nitrogen-containing species is still not well understood, despite the fact that ammonia is an abundant constituent of interstellar ices towards young stellar objects and quiescent molecular clouds. This is mainly because of the lack of dedicated laboratory studies. The aim of this work is to experimentally investigate the formation routes of NH3 and HNCO through non-energetic surface reactions in interstellar ice analogues under fully controlled laboratory conditions and at astrochemically relevant temperatures. This study focuses on the formation of NH3 and HNCO in CO-rich (non-polar) interstellar ices that simulate the CO freeze-out stage in dark interstellar cloud regions, well before thermal and energetic processing start to become relevant. We demonstrate and discuss the surface formation of solid HNCO through the interaction of CO molecules with NH radicals – one of the intermediates in the formation of solid NH3 upon sequential hydrogenation of N atoms. The importance of HNCO for astrobiology is discussed. [ABSTRACT FROM AUTHOR] more...
- Published
- 2015
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40. Relevance of the H2 + O reaction pathway for the surface formation of interstellar water.
- Author
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Lamberts, T., Cuppen, H. M., Fedoseev, G., Ioppolo, S., Chuang, K. -J., and Linnartz, H.
- Subjects
MOLECULAR clouds ,INTERPLANETARY dust ,ASTROCHEMISTRY ,HYDROGENATION ,DARK matter ,COSMIC abundances ,MONTE Carlo method - Abstract
The formation of interstellar water is commonly accepted to occur on the surfaces of icy dust grains in dark molecular clouds at low temperatures (10-20 K), involving hydrogenation reactions of oxygen allotropes. As a result of the large abundances of molecular hydrogen and atomic oxygen in these regions, the reaction H
2 + O has been proposed to contribute significantly to the formation of water as well. However, gas-phase experiments and calculations, as well as solid-phase experimental work contradict this hypothesis. Here, we use precisely executed temperature-programmed desorption (TPD) experiments in an ultra-high vacuum setup combined with kinetic Monte Carlo simulations to establish an upper limit of the water production starting from H2 and O. These reactants were brought together in a matrix of CO2 in a series of (control) experiments at different temperatures and with different isotopological compositions. The water detected with the quadrupole mass spectrometer upon TPD was found to originate mainly from contamination in the chamber itself. However, if water is produced in small quantities on the surface through H2 + O, this can only be explained by a combined classical and tunneled reaction mechanism. An absolutely conservative upper limit for the reaction rate was derived with a microscopic kinetic Monte Carlo model that converts the upper limit into the highest possible reaction rate. Incorporating this rate into simulation runs for astrochemically relevant parameters shows that the upper limit to the contribution of the reaction H2 + O in OH, and hence water formation, is 11% in dense interstellar clouds. Our combined experimental and theoretical results indicate, however, that this contribution is most likely much lower. [ABSTRACT FROM AUTHOR] more...- Published
- 2014
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41. Solid state chemistry of nitrogen oxides – Part II: surface consumption of NO2.
- Author
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Ioppolo, S., Fedoseev, G., Minissale, M., Congiu, E., Dulieu, F., and Linnartz, H.
- Abstract
Nitrogen oxides are considered to be important astrochemical precursors of complex species and prebiotics. However, apart from the hydrogenation of solid NO that leads to the surface formation of hydroxylamine, little is known about the full solid state reaction network involving both nitrogen and oxygen. Our study is divided into two papers, hereby called Part I and Part II. In the accompanying paper, we investigate the surface reactions NO + O/O
2 /O3 and NO + N with a focus on the formation of NO2 ice. Here, we complement this study by measurements of the surface destruction of solid NO2 , e.g., NO2 + H/O/N. Experiments are performed in two separate ultra-high vacuum setups and therefore under different experimental conditions to better constrain the experimental results. Surface reaction products are monitored by means of Fourier Transform Reflection Absorption Infrared Spectroscopy (FT-RAIRS) and Temperature Programmed Desorption (TPD) techniques using mass spectrometry. The surface destruction of solid NO2 leads to the formation of a series of nitrogen oxides such as NO, N2 O, N2 O3 , and N2 O4 as well as HNO, NH2 OH, and H2 O. When NO2 is mixed with an interstellar more relevant apolar (i.e., CO) ice, solid CO2 and HCOOH are also formed due to interactions between different reaction routes. The astrophysical implications of the full nitrogen and oxygen reaction network derived from Parts I and II are discussed. [ABSTRACT FROM AUTHOR] more...- Published
- 2014
- Full Text
- View/download PDF
42. Solid state chemistry of nitrogen oxides – Part I: surface consumption of NO.
- Author
-
Minissale, M., Fedoseev, G., Congiu, E., Ioppolo, S., Dulieu, F., and Linnartz, H.
- Abstract
The role of nitrogen and oxygen chemistry in the interstellar medium is still rather poorly understood. Nitric oxide, NO, has been proposed as an important precursor in the formation of larger N- and O-bearing species, such as hydroxylamine, NH
2 OH, and nitrogen oxides, NO2 and N2 O. The topic of this study is the solid state consumption of NO via oxygenation and the formation of NO2 and other nitrogen oxides (ONNO2 and N2 O4 ) under conditions close to those encountered on icy grains in quiescent interstellar clouds. In our experiments nitric oxide and oxygen allotropes (O, O2 , and O3 ) or N atoms are co-deposited under ultra-high vacuum conditions on different substrates (silicate, graphite, compact ASW ice, and gold) at temperatures ranging between 10 and 35 K. Reaction products are monitored via Fourier Transform Reflection Absorption Infrared Spectroscopy (FT-RAIRS) and Temperature Programmed Desorption (TPD) using mass spectrometry. We find that NO2 is efficiently formed in NO + O/O2 /O3 /N solid surface reactions. These are essentially barrier free and offer a pathway for the formation of NO2 in space. Nitrogen dioxide, however, has not been astronomically detected, contradicting the efficient reaction channel found here. This is likely due to other pathways, including regular hydrogenation reactions, as discussed separately in part II of this study. [ABSTRACT FROM AUTHOR] more...- Published
- 2014
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- View/download PDF
43. DYNAMICS OF CO IN AMORPHOUS WATER-ICE ENVIRONMENTS.
- Author
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Karssemeijer, L. J., Ioppolo, S., Hemert, M. C. van, Avoird, A. van der, Allodi, M. A., Blake, G. A., and Cuppen, H. M.
- Subjects
- *
CARBON monoxide , *ADSORPTION (Chemistry) , *ICE , *NANOPORES , *BINDING sites , *MONTE Carlo method - Abstract
The long-timescale behavior of adsorbed carbon monoxide on the surface of amorphous water ice is studied under dense cloud conditions by means of off-lattice, on-the-fly, kinetic Monte Carlo simulations. It is found that the CO mobility is strongly influenced by the morphology of the ice substrate. Nanopores on the surface provide strong binding sites, which can effectively immobilize the adsorbates at low coverage. As the coverage increases, these strong binding sites are gradually occupied leaving a number of admolecules with the ability to diffuse over the surface. Binding energies and the energy barrier for diffusion are extracted for various coverages. Additionally, the mobility of CO is determined from isothermal desorption experiments. Reasonable agreement on the diffusivity of CO is found with the simulations. Analysis of the 2152 cm–1 polar CO band supports the computational findings that the pores in the water ice provide the strongest binding sites and dominate diffusion at low temperatures. [ABSTRACT FROM AUTHOR] more...
- Published
- 2014
- Full Text
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44. THz and mid-IR spectroscopy of interstellar ice analogs: methyl and carboxylic acid groups.
- Author
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Ioppolo, S., McGuire, B. A., Allodi, M. A., and Blake, G. A.
- Abstract
A fundamental problem in astrochemistry concerns the synthesis and survival of complex organic molecules (COMs) throughout the process of star and planet formation. While it is generally accepted that most complex molecules and prebiotic species form in the solid phase on icy grain particles, a complete understanding of the formation pathways is still largely lacking. To take full advantage of the enormous number of available THz observations (e.g., Herschel Space Observatory, SOFIA, and ALMA), laboratory analogs must be studied systematically. Here, we present the THz (0.3–7.5 THz; 10–250 cm
−1 ) and mid–IR (400–4000 cm−1 ) spectra of astrophysically-relevant species that share the same functional groups, including formic acid (HCOOH) and acetic acid (CH3 COOH), and acetaldehyde (CH3 CHO) and acetone ((CH3 )2 CO), compared to more abundant interstellar molecules such as water (H2 O), methanol (CH3 OH), and carbon monoxide (CO). A suite of pure and mixed binary ices are discussed. The effects on the spectra due to the composition and the structure of the ice at different temperatures are shown. Our results demonstrate that THz spectra are sensitive to reversible and irreversible transformations within the ice caused by thermal processing, suggesting that THz spectra can be used to study the composition, structure, and thermal history of interstellar ices. Moreover, the THz spectrum of an individual species depends on the functional group(s) within that molecule. Thus, future THz studies of different functional groups will help in characterizing the chemistry and physics of the interstellar medium (ISM). [ABSTRACT FROM AUTHOR] more...- Published
- 2014
- Full Text
- View/download PDF
45. Solid CO2 in low-mass young stellar objects Comparison between Spitzer and laboratory spectra.
- Author
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Ioppolo, S., Sangiorgio, I., Baratta, G. A., and Palumbo, M. E.
- Subjects
- *
INTERSTELLAR medium , *ULTRAVIOLET photolysis , *IRRADIATION , *COSMIC rays , *CARBON dioxide , *INFRARED spectroscopy - Abstract
Context. Solid interstellar CO2 is an abundant component of ice dust mantles. Its ubiquity towards quiescent molecular clouds, as well as protostellar envelopes, has recently been confirmed by the IRS (InfraRed Spectrograph) aboard the Spitzer Space Telescope. Although it has been shown that CO2 cannot be efficiently formed in the gas phase, the CO2 surface formation pathway is still unclear. To date several CO2 surface formation mechanisms induced by energetic (e.g., UV photolysis and cosmic ray irradiation) and nonenergetic (e.g., cold atom addition) input have been proposed. Aims. Our aim is to investigate the contribution of cosmic ray irradiation to the formation of CO2 in different regions of the interstellar medium (ISM). To achieve this goal we compared quantitatively laboratory data with the CO2 bending mode band profile observed towards several young stellar objects (YSOs) and a field star by the Spitzer Space Telescope. Methods. All the experiments presented here were performed at the Laboratory for Experimental Astrophysics in Catania (Italy). The interstellar relevant samples were all irradiated with fast ions (30-200 keV) and subsequently annealed in a stainless steel high vacuum chamber (P < 10-7 mbar). Chemical and structural modifications of the ice samples were monitored by means of infrared spectroscopy. Laboratory spectra were then used to fit some thirty observational spectra. Results. A qualitative analysis shows that a good fit can be obtained with a minimum of two components. The choice of the laboratory components is based on the chemical-physical condition of each source. A quantitative analysis of the sources with known visual extinction (AV) and methanol abundances highlights that the solid carbon dioxide can be efficiently and abundantly formed after ion irradiation of interstellar ices in all the selected YSOs in a time compatible with cloud lifetimes (3 × 107 years). Only in the case of field stars can the expected CO2 column density formed upon energetic input not explain the observed abundances. This result, to be confirmed along the line of sight to different quiescent clouds, gives an indirect indication that CO2 can also be formed in an early cloud stage through surface reactions induced by non-energetic mechanisms. In a later stage, when ices are exposed to higher UV and cosmic ray doses, the CO2 total abundance is strongly affected by energetic formation mechanisms. Conclusions. Our results indicate that energetic processing of icy grain mantles significantly contribute to the formation of solid phase interstellar CO2. [ABSTRACT FROM AUTHOR] more...
- Published
- 2013
- Full Text
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46. Nitrogen oxides and carbon chain oxides formed after ion irradiation of CO:N2 ice mixtures.
- Author
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Sicilia, D., Ioppolo, S., Vindigni, T., Baratta, G. A., and Palumbo, M. E.
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NITROGEN oxides , *CARBON oxides , *IONS , *ICE sheets , *ULTRAVIOLET radiation , *LOW temperatures - Abstract
Context. High CO depletion as well as depletion of N-bearing species is observed in dense pre-stellar cores. It is generally accepted that depleted species freeze out onto dust grains to form icy mantles and that these ices suffer energetic processing due to cosmic ion irradiation and ion-induced UV photons. Aims. The aim of this work is to study the chemical and structural effects induced by ion irradiation on different CO:N2 mixtures at low temperature (16 K) to simulate the effects of cosmic ion irradiation of icy mantles. Methods. Different CO:N2 mixtures and pure CO and pure N2 were irradiated with 200 keV H+ at 16 K. Infrared transmittance spectra of the samples were obtained in situ before and after irradiation. The samples were warmed up and spectra were taken at different temperatures. The residues left over on the substrate at room temperature were analysed ex situ by micro Raman spectroscopy. Results. Several new absorption features are present in the infrared spectra after irradiation, indicating that new species are formed. The most abundant are nitrogen oxides (such as NO, NO2 and N2O), carbon chain oxides (such as C2O, C3O and C3O2), carbon chains (such as C3 and C6), O3 and N3. A refractory residue is also formed after ion irradiation and is clearly detected by Raman spectroscopy. Conclusions. We suggest that carbon chains and nitrogen oxides observed in the gas phase towards star-forming regions are formed in the solid phase after cosmic ion irradiation of icy grain mantles and are released into the gas phase after desorption of grain mantles. We expect that the Atacama Large Millimeter/submillimeter Array (ALMA), thanks to its high sensitivity and resolution, will increase the number of nitrogen oxides and carbon chain oxides detected towards star-forming regions. [ABSTRACT FROM AUTHOR] more...
- Published
- 2012
- Full Text
- View/download PDF
47. Surface formation of CO.
- Author
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Ioppolo, S., van Boheemen, Y., Cuppen, H. M., van Dishoeck, E. F., and Linnartz, H.
- Subjects
- *
CARBON monoxide , *LOW temperatures , *DISSOCIATION (Chemistry) , *HYDROGENATION , *INTERSTELLAR medium , *RADICALS (Chemistry) , *INFRARED spectroscopy , *ASTRONOMICAL observations - Abstract
The surface formation of CO at low temperatures through the reaction CO + OH and direct dissociation of the resulting HO-CO complex is shown by hydrogenation of a CO:O ice mixture. Such a binary ice is not fully representative for an interstellar ice, but the hydrogenation of O ice produces OH radicals, which allows the investigation of the interstellar relevant CO + OH solid state reaction under fully controlled laboratory conditions. Similar recent astrophysical ice studies have focused on the investigation of isolated surface reaction schemes, starting from the hydrogenation of pure ices, like solid CO or O. For such ices, no CO formation is observed upon H-atom exposure. The hydrogenation of binary ice mixtures presented here allows to investigate for the first time the influence of the presence of other species in the ice on the pure ice reaction shemes. Mixtures of CO:O are deposited on a substrate in an ultra high vacuum setup at low temperatures (15 and 20 K) and subsequently hydrogenated. The ice is monitored by means of Reflection Absorption InfraRed Spectroscopy (RAIRS). Results show that solid CO is formed in all studied CO:O mixtures under our laboratory conditions. Within the experimental uncertainties no dependency on ice temperature or composition is observed. The laboratory results show a correlation between the formation of CO and HO, which is consistent with the astronomical observation of solid CO in water-rich environments. The results also show that the contemporary presence of CO and O molecules in the ice influences the final product yields of the separate CO + H (HCO, CHOH) and O+ H (HO and HO) channels, even though the formation rates are not significantly affected. [ABSTRACT FROM AUTHOR] more...
- Published
- 2011
- Full Text
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48. Surface formation of HCOOH at low temperature.
- Author
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Ioppolo, S., Cuppen, H. M., van Dishoeck, E. F., and Linnartz, H.
- Subjects
- *
FORMIC acid , *INTERSTELLAR medium , *LOW temperatures , *SOLID state chemistry , *CARBON dioxide , *OXYGEN , *FOURIER transform infrared spectroscopy , *HYDROGENATION , *COSMOCHEMISTRY - Abstract
ABSTRACT The production of formic acid (HCOOH) in cold and hot regions of the interstellar medium is not well understood. Recent gas-phase experiments and gas-grain models hint at a solid-state production process at low temperatures. Several surface reaction schemes have been proposed in the past decades, even though experimental evidence for their efficiency was largely lacking. The aim of this work is to give the first experimental evidence for an efficient solid-state reaction scheme providing a way to form HCOOH under astronomical conditions. Several surface reaction channels have been tested under fully controlled experimental conditions by using a state-of-the-art ultrahigh vacuum set-up through co-deposition of H atoms and CO:O2 mixtures with 4:1, 1:1 and 1:4 ratios. During deposition spectral changes in the ice are monitored by means of a Fourier transform infrared (FTIR) spectrometer in reflection absorption infraRed (RAIR) mode. After co-deposition a temperature programmed desorption (TPD) experiment is performed and gas-phase molecules are detected by a quadrupole mass spectrometer (QMS). Formation of HCOOH is observed at low temperatures mainly through hydrogenation of the HO-CO complex, while reactions with the HCO radical as intermediate are found to be inefficient. The HO-CO complex channel, which was previously not considered as an important HCOOH formation route, can explain the presence of HCOOH in dense cold clouds, at the beginning of the warm-up phase of a protostar, and, therefore, is likely to be astrochemically relevant. [ABSTRACT FROM AUTHOR] more...
- Published
- 2011
- Full Text
- View/download PDF
49. Water formation at low temperatures by surface O2hydrogenation II: the reaction network.
- Author
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Cuppen, H. M., Ioppolo, S., Romanzin, C., and Linnartz, H.
- Abstract
Water is abundantly present in the Universe. It is the main component of interstellar ice mantles and a key ingredient for life. Water in space is mainly formed through surface reactions. Three formation routes have been proposed in the past: hydrogenation of surface O, O2, and O3. In a previous paper [Ioppolo et al., Astrophys. J., 2008, 686, 1474] we discussed an unexpected non-standard zeroth-order H2O2production behaviour in O2hydrogenation experiments, which suggests that the proposed reaction network is not complete, and that the reaction channels are probably more interconnected than previously thought. In this paper we aim to derive the full reaction scheme for O2surface hydrogenation and to constrain the rates of the individual reactions. This is achieved through simultaneous H-atom and O2deposition under ultra-high vacuum conditions for astronomically relevant temperatures. Different H/O2ratios are used to trace different stages in the hydrogenation network. The chemical changes in the forming ice are followed by means of reflection absorption infrared spectroscopy (RAIRS). New reaction paths are revealed as compared to previous experiments. Several reaction steps prove to be much more efficient (H + O2) or less efficient (H + OH and H2+ OH) than originally thought. These are the main conclusions of this work and the extended network concluded here will have profound implications for models that describe the formation of water in space. [ABSTRACT FROM AUTHOR] more...
- Published
- 2010
- Full Text
- View/download PDF
50. Water formation at low temperatures by surface O2hydrogenation I: characterization of ice penetration.
- Author
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Ioppolo, S., Cuppen, H. M., Romanzin, C., van Dishoeck, E. F., and Linnartz, H.
- Abstract
Water is the main component of interstellar ice mantles, is abundant in the solar system and is a crucial ingredient for life. The formation of this molecule in the interstellar medium cannot be explained by gas-phase chemistry only and its surface hydrogenation formation routes at low temperatures (O, O2, O3channels) are still unclear and most likely incomplete. In a previous paper we discussed an unexpected zeroth-order H2O production behavior in O2ice hydrogenation experiments compared to the first-order H2CO and CH3OH production behavior found in former studies on hydrogenation of CO ice. In this paper we experimentally investigate in detail how the structure of O2ice leads to this rare behavior in reaction order and production yield. In our experiments H atoms are added to a thick O2ice under fully controlled conditions, while the changes are followed by means of reflection absorption infrared spectroscopy (RAIRS). The H-atom penetration mechanism is systematically studied by varying the temperature, thickness and structure of the O2ice. We conclude that the competition between reaction and diffusion of the H atoms into the O2ice explains the unexpected H2O and H2O2formation behavior. In addition, we show that the proposed O2hydrogenation scheme is incomplete, suggesting that additional surface reactions should be considered. Indeed, the detection of newly formed O3in the ice upon H-atom exposure proves that the O2channel is not an isolated route. Furthermore, the addition of H2molecules is found not to have a measurable effect on the O2reaction channel. [ABSTRACT FROM AUTHOR] more...
- Published
- 2010
- Full Text
- View/download PDF
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