Tag: ta2.11

20-EPN-084: Converting one amino acid to the other containing sulfur via ion irradiation : Implication to chemical evolution on Europa surface ices

Visit by Rahul Kumar Kushwaha, Physical Research Laboratory, Ahmedabad (India) to TA2.11 Atomki Ice Chamber for Astrophysics / Astrochemistry (ICA) (Hungary).
Dates of visit: 8-19 December 2021

Report Summary: The non-equilibrium chemistry driven by the charged particle and photon irradiation processes are responsible for the rich chemistry on the surfaces of icy satellites. Among the icy satellites of the Jovian and Saturnian planetary systems, a few satellites such as Ganymede, Europa, Dione, Rhea, Callisto and Titan that are embedded in their respective planetary magnetospheres were observed to undergo rich chemical processes due to the bombardment of a wide range of energetic atomic and molecular ions that are present in their planet’s magnetospheres, which processes the icy surfaces of satellites by irradiation and implantation. Magnetospheres also help in bringing new species from one satellite to the other. Especially in the Jupiter system of icy satellites, sulfur transfer from Io to the other satellites is quite likely. The sulfur ions from Io are picked up by the magnetosphere and are accelerated towards the other icy satellites; Europa being the closest neighbour to Io will be implanted with sulfur ions. The Jovian satellites, due to the presence of the Jupiter’s magnetosphere, are subjected to highly energetic S ion irradiation which leads to a range of chemical activity on their surfaces. In this project, we have studied the effect of S ion irradiation on Aspartic acid for a range of energies at two different temperatures (100 K, 20 K), where the 100 K experiments are aimed to mimic the conditions of Europa. The irradiated residue was then analysed using an optical microscope, scanning electron microscope and liquid chromatography mass spectrometry.

Full scientific report published by kind permission of Rahul Kumar Kushwaha

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20-EPN-016: Formation and fate of methyl formate isomers in space

Virtual visit by Dr Sergio Ioppolo (Queen Mary University of London, UK) to TA2.11 Atomki Ice Chamber for Astrophysics / Astrochemistry (ICA) (Hungary).
Dates of visit: 12 October 2020 – 31 March 2021

Report Summary: All isomers of C₂H₄O₂, i.e. glycolaldehyde (HCOCH₂OH), acetic acid (CH₃COOH) and methyl formate (HCOOCH₃), have been observed abundantly around the Galactic center, in dark clouds, and hot cores of the interstellar medium (ISM), as well as in some minor ice objects of the Solar System. However, their exact gas-grain formation and destruction pathway is still under debate. According to El-Abd et al. (2019), the observed column densities of methyl formate and acetic acid are well-correlated, and are likely simply tracking the relative total gas mass in star forming regions. Methyl formate and glycolaldehyde, however, display a stark dichotomy in their relative column densities. The latter findingsuggests that different formation/destruction routes are at play for the three isomers. To date, there is a strong laboratory evidence for an efficient production of glycolaldehyde, methyl formate, and acetic acid in the ISM (Gerakines et al. 1996; Bennett and Kaiser 2007; Modica et al. 2012).

During the TA 20-EPN-016 at the ion accelerator facility Atomki in Debrecen (Hungary), we have performed a systematic set of experiments using the novel ultrahigh vacuum ICA end station to investigate the formation and destruction pathways of C₂H₄O₂ isomers and a variety of other interstellar complex organic molecules. The experimental campaign revealed to be successful as all the planned experiments were performed. Results aided the design of new potential key experiments that will be included in a future follow-up beamtime bid at the facility.

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20-EPN-005: Cosmic-ray-induced chemistry in pure ices

Virtual visit by Alexei Ivlev, Max Planck Institute for Extraterrestrial Physics (MPE) (Germany) to TA2.11 Atomki Ice Chamber for Astrophysics / Astrochemistry (ICA) (Hungary).
Dates of visit: 23 February – 05 July 2021

Report Summary: The principal aim of the project was a dedicated study of generic effects induced in pure astrophysical ice analogs due to their bombardment by cosmic rays with energies E in the vicinity of the maximum of electronic stopping power. It is known that the energy of ejected electrons, which are produced in primary ionization events, has a significant dependence on E in this energy range. 

Thus, by selecting pairs of beam energies on both sides of the Bragg peak, such that the corresponding stopping-power values are equal, we were able to probe the effect of electron-impact excitations of ice molecules. We selected CO films as the best irradiation target, for which the biggest variety of radiolysis products was expected and the most detailed predictions of chemical models were available. 

We found that the first radiolysis products, detected at the astrophysically relevant values of ion fluence, are very different from predictions of chemical models. At the same time, the reaction kinetics shows no statistically significant difference between ion beams of same stopping power. This rules out the importance of electron-impact excitation in radiolysis chemistry of CO, and suggests that this process may generally be negligible compared to the chemistry driven by CR heating (determined by the stopping power value). On the other hand, by comparing the sputtering yields measured for beams of same stopping power, we discovered a significant asymmetry, with the yield at lower energies being up to a factor of two larger that at higher energies.

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20-EPN-043: A Systematic Study of Sulfur Ion Radiolysis of Simple Oxide Ices.

Visit by Zuzana Kanuchova (virtual participation), Astronomical Institute od Slovak Academy of Sciences (Slovakia) and Duncan Mifsud (in-person participation), University of Kent (UK) to TA2.11 Atomki Ice Chamber for Astrophysics / Astrochemistry (ICA) (Hungary).
Dates of visit: 30 November – 4 December 2020 and 25-29 January 2021

Report Summary: We have implanted 290 keV S⁺ ions in a variety of simple oxide ices, including CO, CO₂, H₂O, N₂O, O₂, and CO:N₂O at 20 K, as well as CO₂ and H₂O at 70 K. Our aim was to determine whether such implantations could result in the formation of sulfur-bearing product molecules, particularly SO₂ which has been detected at the surfaces of several icy Solar System moons. 

The performed experiments suffered from initial setbacks in the form of unexpected and significant sputtering of the astrophysical ice analogues during irradiation. In order to mitigate this sputtering, we made use of two different experimental techinques; (i) via simultaneous deposition and irradiation of the ice analogue in cases where we knew gas phase chemistry to be negligible, and (ii) via creation of a very thick (~3-5 μm) ice and a slow rate of implantation. Once these initial problems were solved, we were able to successfully carry out implantations into the six ices mentioned above. 

Our work has indicated that although sulfur-bearing molecules (such as OCS and H₂SO₄ hydrates) may form as a result of such implantations, SO₂ formation was not detected in most experiments, except at high fluence (~1016 ions/cm²) implantations in CO. Such results have important implications for the icy Galilean satellites of Jupiter, suggesting that the SO₂ present there may be formed by endogenic processes at the lunar surfaces.

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20-EPN-032: Radioresistance of aromatic complex organic molecules: nucleobases.

Virtual visit by Hermann Rothard, CIMAP (Caen, F) CNRS (France) to TA2.11 Atomki Ice Chamber for Astrophysics / Astrochemistry (ICA) (Hungary).
Dates of visit: 17 May – 02 July 2021

Report Summary: Complex molecules (including amino acids and nucleobases) can be formed in cold space environments conditions (e.g. dense molecular clouds, outer solar system) by e.g. UV irradiation and ion bombardment of ices containing simple molecules. Consequently, the radiation resistance of such complex molecules in order to determine their survival times in space should be investigated. We therefore studied the radiolysis and radio-resistance of the purine nucleobase (Adenine, two aromatic rings) in solid phase as a function of temperature (20-300 K) with H (0.8 MeV) and He (3.2 MeV) beams at ATOMKI. This first systematic study of the influence of the temperature revealed that Adenine is found to be significantly (of the order of 50%) more radio-resistant at high temperatures. At low temperatures T < 50K, Adenine is more radiosensitive (higher cross sections).

The results are preliminary and analysis is ongoing. Furthermore, we found that the destruction cross sections scales with the electronic stopping stopping following a power law with a stronger than linear dependence.

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