X-RAY IRRADIATION OF H₂O + CO ICE MIXTURES WITH SYNCHROTRON LIGHT

Abstract

We irradiated a (4:1) mixture of water and carbon monoxide with soft X-rays of energies up to 1.2 keV. The experiments were performed using the spherical grating monochromator beamline at National Synchrotron Radiation Research Center in Taiwan. Both monochromatic (300 and 900 eV) and broader energy fluxes (250–1200 eV) were employed. During the irradiation, the H2O + CO mixture was ionized, excited, and fragmented, producing a number of reactive species. The composition of the ice has been monitored throughout both the irradiation and warm-up phases. We identified several products, which can be related through a plausible chemical reaction scheme. Such chemistry is initiated by the injection of energetic photoelectrons that produce multiple ionization events generating a secondary electron cascade. The results have been discussed in light of a model for protoplanetary disks around young solar-type stars.

Photochemistry and desorption induced by X-rays in water rich astrophysical ice analogs: implications for the moon Enceladus and other frozen space environments

“…Additionally, in spite of the current datasets be representative and are in good agreement with previous experiments on irradiating of astrophysical ice analogs by strong ionizing radiation, 10,16,[23][24][25][29][30][31][32]46,49,50 additional experiments increasing the dataset at larger uences help to decrease uncertainties in the determination of F E . Future experiment may also investigate different temperatures and radiation ux to extend the current work and better clarify the chemical equilibrium scenario, an important stage for ices irradiated at astrophysical environments.…”

“…Previous experiments also employing X-rays on analogous astrophysical ices have also shown the importance of such ionizing agent in the physicochemical processing of the frozen sample. 10,[21][22][23][24][25][26] Section 2 describes the experimental setup and sample properties. The results and the analysis of the infrared spectra of both samples are given the Section 3.…”

Synthesis of Complex Organic Molecules in Soft X-Ray Irradiated Ices

“…Formation routes, mechanisms responsible for the production of new species, and efficiency of the different energetic processing have contributed to the interpretation of the observed interstellar ice features (Boogert et al 2015). More recently X-ray processing of ice analogues has been studied given its relevance in circumstellar discs around young stars Andrade et al 2010;Ciaravella et al 2012;Jiménez-Escobar et al 2012;Chen et al 2013;Pilling & Bergantini 2015;Ciaravella et al 2016;Jiménez-Escobar et al 2016, 2018. In solar type stars X-ray emission dominates over far extreme ultraviolet emissions for almost one billion year (Ribas et al 2005) penetrating through the disc and reaching inner regions otherwise forbidden to less energetic photons (e.g., Walsh et al 2012).…”

Reactions of Photoionization-Induced CO–H2O Cluster: Direct Ab Initio Molecular Dynamics Study

“…A number of experiments have been carried out in mixtures of CO–H 2 O systems. 22 − 25 The HOCO radical was detected as one of the products in these experiments. Therefore, the study of the formation mechanism of HOCO is strongly correlated to the elucidation of the chemical evolution in the universe.…”