Browsing by Author "Severin, Daniel"

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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.
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.