Browsing by Author "Domaracka, Alicja"

Now showing 1 - 11 of 11

Chemical reactions in H2O:CO interstellar ice analogs promoted by energetic heavy ion irradiation
(2022) Barros, Ana; Mejía Guamán, Christian Fernando; Seperuelo Duarte, Eduardo; Domaracka, Alicja; Boduch, Philippe; Rothard, Hermann; Da Silveira, Enio Frota
H2O:CO, at concentrations of (3:2) and (10:1), was condensed on CsI substrate at 15 K and irradiated with 46 MeV 58Ni11 + ion beam. Radiolysis induced by fast heavy ions was analyzed by infrared spectroscopy (FTIR). The formation of nine molecular species, CO2, H2O2, HCOOH, HCO, H2CO, 13CO2, CH3OH, O3 and C3O2 was observed. For both concentrations, carbon dioxide (CO2), formaldehyde (H2CO), formic acid (HCOOH), and hydrogen peroxide (H2O2) are the most abundant products species, and tricarbon dioxide (C3O2) is much less abundant. Precursor destruction cross sections and formation cross sections of products are determined. The CO destruction cross section for the (3:2) concentration is almost five times higher than that of water, while those for the (10:1) concentration are practically the same. Atomic sputtering yields are estimated for the two ice films, the total mass sputtered is approximately 2.5 × 106 u per impact. These results contribute to figure out the chemical pathways of compounds synthesized from the two most abundant organic species (H2O and CO) observed in the ices of grain mantles of the circumstellar envelopes and interstellar medium. In additional, the finding results reveal that molecular astronomical percentages are comparable to those obtained after 15 eV molec−1 of deposited dose in current experiments compared with the relative concentration of molecules in solid phase observed in MYSO, LYSO, BG Stars, and Comets.
Compaction of porous ices rich in water by swift heavy ions
(2015) Mejía Guamán, Christian Fernando; Ferreira de Barros, Ana Lucía; Seperuelo Duarte, Eduardo; Da silveira, Énio Frota; Dartois, Emmanuel; Domaracka, Alicja; Rothard, Hermann; Boduch, Philippe
Porous water ice and water ice mixtures H2O:X (X = CO, CO2 and CH4) produced at 15 K, with film thicknesses in the 0.5–1 μm range, were irradiated by swift ions and monitored by mid-infrared spectroscopy (FTIR). The analysis of the evolution of the pure water ice infrared absorption on ion beam dose reveals a strong correlation among three quantities: (i) the absorbance of the most intense band (3250 cm−1), (ii) the wavelength of the maximum absorbance of this band and (iii) the absorbance of the OH-dangling bonds. This correlation is interpreted as indications of the water ice compaction by irradiation: as the beam fluence increases, the ice porosity decreases, the dangling bond peaks collapse and the area and position of the 3250 cm−1 band vary exponentially, all of them evolving with the same compaction cross section (). The linear dependence ( being the electronic stopping power) is observed for both pure and mixed water ices, confirming previous results. We suggests that the infrared absorption A-value varies with dose as during the compaction process ( eV/molec being the effective energy density to eliminate the OH-db, and is a parameter characterizing the porosity). These findings may be used as a diagnostic tool to probe the morphology of water ices occurring in the outer Solar System and in the ISM.
Cosmic ray–ice interaction studied by radiolysis of 15 K methane ice with MeV O, Fe and Zn ions
(2013) Rothard, Hermann; Mejía Guamán, Christian Fernando; Ferreira De Barros, Ana Lucía; Bordalo, Vinicius; Frota Da Silveira, Enio; Boduch, Philippe; Domaracka, Alicja
Methane (CH4) ice is found in the interstellar medium and in several bodies of the Solar system, where it is commonly exposed to cosmic rays and stellar winds. The chemical, physical and structural effects induced by fast heavy ions in thin layers of pure CH4 ices at 15 K are analysed by mid-infrared spectroscopy (Fourier transform infrared). Different pure CH4 ice samples were irradiated with 6 MeV 16O2, 220 MeV 16O7, 267 MeV 56Fe22 and 606 MeV 70Zn26 ions at Grand Accélérateur National d’Ions Lourds/France. Results show that CnHm molecules, where n = 2–4 and m = 2(n − 1) to 2(n + 1) and radical species CH3, C2H3 and C2H5 are formed. The destruction cross-sections of CH4 ice and the formation cross-sections of new molecules CnHm are reported. The extrapolation of current results allow us to estimate the half lives of CH4 ices in the interstellar medium and the Solar system (Earth orbit) as about 600 x 106 and 600 yr, respectively. This huge ratio strongly suggests that the vast majority of chemical or even biochemical processes induced by ionizing radiation occur close to stars.
Irradiation of nitrogen-rich ices by swift heavy ions: clues for the formation of ultracarbonaceous micrometeorites
(2015) Mejía Guamán, Christian Fernando; Martinez Rodrigues, Rafael; Dartois, Emmanuel; Vignoli Muniz, Gabriel S.; Engrand, Cecile; Godard, Marie; Delauche, L.; Auge, Basile; Bardin, Nathalie; Rothard, H.; Boduch, Philippe; Domaracka, Alicja; Duprat, Jean
Context. Extraterrestrial materials, such as meteorites and interplanetary dust particles, provide constraints on the formation and evolution of organic matter in the young solar system. Micrometeorites represent the dominant source of extraterrestrial matter at the Earth’s surface, some of them originating from large heliocentric distances. Recent analyses of ultracarbonaceous micrometeorites recovered from Antarctica (UCAMMs) reveal an unusually nitrogen-rich organic matter. Such nitrogen-rich carbonaceous material could be formed in a N2-rich environment, at very low temperature, triggered by energetic processes. Aims. Several formation scenarios have been proposed for the formation of the N-rich organic matter observed in UCAMMs. We experimentally evaluate the scenario involving high energy irradiation of icy bodies subsurface orbiting at large heliocentric distances. Methods. The effect of Galactic cosmic ray (GCR) irradiation of ices containing N2 and CH4 was studied in the laboratory. The N2-CH4 (90:10 and 98:2) ice mixtures were irradiated at 14 K by 44 MeV Ni11+ and 160 MeV Ar15+ swift heavy ion beams. The evolution of the samples was monitored using in-situ Fourier transform infrared spectroscopy. The evolution of the initial ice molecules and new species formed were followed as a function of projectile fluence. After irradiation, the target was annealed to room temperature. The solid residue of the whole process left after ice sublimation was characterized in-situ by infrared spectroscopy, and the elemental composition was measured ex-situ. Results. The infrared bands that appear during irradiation allow us to identify molecules and radicals (HCN, CN−, NH3, ...). The infrared spectra of the solid residues measured at room temperature show similarities with that of UCAMMs. The results point towards the efficient production of a poly-HCN-like residue from the irradiation of N2-CH4 rich surfaces of icy bodies. The room temperature residue provides a viable precursor for the N-rich organic matter found in UCAMMs.
Radiolysis and sputtering of carbon dioxide ice induced by swift Ti, Ni, and Xe ions
(2015) Mejía Guamán, Christian Fernando; Bender, M.; Severin, Daniel; Trautmann, Christina; Boduch, Philippe; Bordalo, Vinicius; Domaracka, Alicja; Lv, Xueyang; Martinez, Rafael; Rothard, Hermann
Solid carbon dioxide (CO2) is found in several bodies of the solar system, the interstellar medium (ISM) and young stellar objects, where it is exposed to cosmic and stellar wind radiation. Here, the chemical and physical modifications induced by heavy ion irradiation of pure solid CO2 at low temperature (T = 15–30 K) are analyzed. The experiments were performed with Ti (550 MeV) and Xe (630 MeV) ions at the UNILAC of GSI/Darmstadt and with Ni ions (46 and 52 MeV) at IRRSUD of GANIL/Caen. The evolution of the thin CO2 ice films (deposited on a CsI window) was monitored by mid-infrared absorption spectroscopy (FTIR). The dissociation rate of CO2, determined from the fluence dependence of the IR absorption peak intensity, is found to be proportional to the electronic stopping power Se. We also confirm that the sputtering yield shows a quadric increase with electronic stopping power. Furthermore, the production rates of daughter molecules such as CO, CO3 and O3 were found to be linear in Se.
Radiolysis of carbon-dioxide ice by swift Ti and Xe ions
(2015) Boduch, PHilippe; Domaracka, Alicja; Bordalo, Vinicius; Trautmann, Christina; Mejía Guamán, Christian Fernando; Bender, Markus; Rothard, Hermann; Severin, Daniel; Martínez Rodríguez, Rafael Eduardo; LV, Xue Yang
Ices (H2O, CO, CO2, NH3, ..) are omnipresent in space on comets, the moons of giant planets, dust grains in dense clouds (the birthplaces of stars and planetary systems). They are exposed to cosmic rays, which in turn induce radiolysis, i.e. fragmentation of initial molecules, formation of radicals, and subsequent synthesis of molecules. Even complex pre-biotic molecules such as amino acids can be formed. Due to their high electronic energy loss the heavy ion fraction in cosmic rays yields nonnegligible contributions to sputtering and radiolysis, even if protons and alpha particles are more abundant [1]. Heavy-ion beams from large accelerator facilities are useful to simulate the specific effects induced by the heavy ion fraction of cosmic radiation in the laboratory. We complemented the experiments (550 MeV Ti beams) reported in [2] at the UNILAC M-branch, by irradiation with 630 MeV Xe beams. On-line Fourier transform infrared absorption spectroscopy (FTIR) allowed us to follow molecule destruction and synthesis in CO2 ice deposited at approx. 20 K on a CsI substrate.
Radiolysis of cytosine at cryogenic temperatures by swift heavy ion bombardments
(2022) Agníhotri, Aditya; Vignoli Muniz, Gabriel S.; Domaracka, Alicja; Rothard, Hermann; Martinez, Rafael; Mejía Guamán, Christian Fernando; Boduch, Philippe; Augé, Basile
We investigated the radiolysis effects on the cytosine in the solid phase irradiated by swift heavy ions as galactic cosmic ray analogues (GCRs). Infrared (IR) absorption spectroscopy was employed to monitor the physical and chemical radiolytic modifications. The targets were prepared on ZnSe in two different ways: (1) by dropping a nucleobase-water-ethanol solution on the substrate and evaporating the solvent and (2) by sublimation of nucleobase powders in an oven and condensation on the windows. Both types of samples present similar IR absorption spectra. From the exponential decrease of the areas of IR absorption bands as a function of projectile fluence, apparent destruction cross sections (σd) were determined and were found to be very similar for samples prepared using both techniques. The destruction cross section of solid cytosine at cryogenic temperatures follows an electronic stopping (Se) power law: σd = C Sen, where C is a constant and the exponential n is a dimensionless quantity. We determined σd = (3 ± 1) × 10-17 Se (1.25 ±0.06). New absorption features emerge from cytosine degradation, which can be attributed to OCN-, H2CO, and HNCO. By using the observed power law, the half-life of cytosine exposed to galactic cosmic rays was estimated in the order of Mega years. The findings reported here may help a better understanding of complex organic molecule radiostability.
Radioresistance of adenine to cosmic rays
(2017) Domaracka, Alicja; Rothard, Hermann; Vignoli Muniz, Gabriel S.; Mejía Guamán, Christian Fernando; Martinez, Rafael; Auge, Basile; Boduch, Philippe
The presence of nucleobases in carbonaceous meteorites on Earth is an indication of the existence of this class of molecules in outer space. However, space is permeated by ionizing radiation, which can have damaging effects on these molecules. Adenine is a purine nucleobase that amalgamates important biomolecules such as DNA, RNA, and ATP. Adenine has a unique importance in biochemistry and therefore life. The aim of this work was to study the effects of cosmic ray analogues on solid adenine and estimate its survival when exposed to corpuscular radiation. Adenine films were irradiated at GANIL (Caen, France) and GSI (Darmstadt, Germany) by 820 MeV Kr³³⁺, 190 MeV Ca¹⁰⁺, 92 MeV Xe²³⁺, and 12 MeV C⁴⁺ ion beams at low temperature. The evolution of adenine molecules under heavy ion irradiation was studied by IR absorption spectroscopy as a function of projectile fluence. It was found that the adenine destruction cross section (σd) follows an electronic stopping power (Se) power law under the form: CSeⁿ; C is a constant, and the exponential n is a dimensionless quantity. Using the equation above to fit our results, we determined σd = 4 × 10⁻¹⁷ Se1.17, with Se in kiloelectronvolts per micrometer (keV μm⁻¹). New IR absorption bands arise under irradiation of adenine and can be attributed to HCN, CN⁻, C2H4N4, CH3CN, and (CH3)3CNC. These findings may help to understand the stability and chemistry related to complex organic molecules in space. The half-life of solid adenine exposed to the simulated interstellar medium cosmic ray flux was estimated as (10 ± 8) × 10⁶ years.
Swift heavy ion irradiation of thymine at cryogenic temperature
(2022) Trautmann, Christina; Vignoli Muniz, Gabriel S.; Mejía Guamán, Christian Fernando; Rothard, Hermann; Severin, Daniel; Augé, Basile; Domaracka, Alicja; Boduch, Philippe; Agníhotri, Aditya; Bender, Markus
Thymine (C5H6N2O2) is a basic N-heterocyclic nucleobase in all known organisms, and this molecule is also found in meteoritic materials. This study aims to investigate thymine's physical and chemical modifications under ion irradiation in cryogenic conditions. Space radiation was simulated by exposing thymine at 27 K to 230 MeV 48Ca10+ ions. Fourier transform infrared spectroscopy (FTIR) was employed to monitor the degradation of a 2.8 μm thick sample film under irradiation. From the intensity decrease of the infrared absorptions as a function of ion fluence, the destruction cross-section (σ), required to dissociate or eject a thymine molecule, is deduced by an exponential function. The physical and chemical modifications induced by energetic projectiles can be related to the electronic stopping power Se as σ=Se/D0, where D0=9.6±0.4 eV/molecule is the effective mean dose needed to destroy the thymine molecule at 27 K. Also, new molecular species formed under irradiation are observed and, based on infrared spectra, identified as CN−, OCN−, HCNO, and CO.
Swift heavy ion irradiation of water ice from MeV to GeV energies
(2013) Mejía Guamán, Christian Fernando; Frota Da silveira, Enio; Godard, Marie; Domaracka, Alicja; Chabot, Marin; Brunetto, Rosario; Boduch, Philippe; Ferreira De barros, Ana Lucía; Ding, Jing Jie; Dartois, Enmanuel; Pino, Thomas; Thomas, Jean Charles; Rothard, Hermann
Context. Cosmic ray ion irradiation affects the chemical composition of and triggers physical changes in interstellar ice mantles in space. One of the primary structural changes induced is the loss of porosity, and the mantles evolve toward a more compact amorphous state. Previously, ice compaction was monitored at low to moderate ion energies. The existence of a compaction threshold in stopping power has been suggested. Aims. In this article we experimentally study the effect of heavy ion irradiation at energies closer to true cosmic rays. This minimises extrapolation and allows a regime where electronic interaction always dominates to be explored, providing the ice compaction cross section over a wide range of electronic stopping power. Methods. High-energy ion irradiations provided by the GANIL accelerator, from the MeV up to the GeV range, are combined with in-situ infrared spectroscopy monitoring of ice mantles. We follow the IR spectral evolution of the ice as a function of increasing fluence (induced compaction of the initial microporous amorphous ice into a more compact amorphous phase). We use the number of OH dangling bonds of the water molecule, i.e. pending OH bonds not engaged in a hydrogen bond in the initially porous ice structure as a probe of the phase transition. These high-energy experiments are combined with lower energy experiments using light ions (H, He) from other facilities in Catania, Italy, and Washington, USA. Results. We evaluated the cross section for the disappearance of OH dangling bonds as a function of electronic stopping power. A cross-section law in a large energy range that includes data from different ice deposition setups is established. The relevant phase structuring time scale for the ice network is compared to interstellar chemical time scales using an astrophysical model. Conclusions. The presence of a threshold in compaction at low stopping power suggested in some previous works seems not to be confirmed for the high-energy cosmic rays encountered in interstellar space. Ice mantle porosity or pending bonds monitored by the OH dangling bonds is removed efficiently by cosmic rays. As a consequence, this considerably reduces the specific surface area available for surface chemical reactions.
Swift heavy ion modifications of astrophysical water ice
(2015) Rothard, Hermann; Ding, Jing Jie; Domaracka, Alicja; Da silveira, Énio Frota; Thomas, Jean Charles; Pino, Thomas; Mejía Guamán, Christian Fernando; Dartois, Enmanuel; Basile, Augé; Chabot, Marin; Brunetto, Rosario; Boduch, Philippe; Xue Yang, LV; Ferreira de Barros, Ana Lucia; Godard, Marie; Kamalou, Omar
In the relatively shielded environments provided by interstellar dense clouds in our Galaxy, infrared astronomical observations have early revealed the presence of low temperature (10–100 K) ice mantles covering tiny grain “cores” composed of more refractory material. These ices are of specific interest because they constitute an interface between a solid phase under complex evolution triggered by energetic processes and surface reactions, with a rich chemistry taking place in the gas phase. The interstellar ice mantles present in these environments are immersed, in addition to other existing radiations fields, in a flux of cosmic ray particles that can produce new species via radiolysis processes, but first affects their structure, which may change and also induces desorption of molecules and radicals from these grains. Theses cosmic rays are simulated by swift ions in the laboratory for a better understanding of astrophysical processes.