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| Paper: |
Ionization and Desorption of Molecule Ice Stimulated by X-Rays in
Circumstellar Envelopes |
| Volume: |
464, Circumstellar Dynamics at High Resolution |
| Page: |
361 |
| Authors: |
Mendoza, E. F.; Almeida, G.; Wolff, W.; Andrade, D. P. P.; Rocco, M. L. M.; Boechat-Roberty, H. M. |
| Abstract: |
The HCN and C2H2 molecules present in protoplanetary disks can form the
Nitrogen-containing cyclic organic molecules (N-heterocycles) that play
important roles in terrestrial biology, for example as the nucleobases in
genetic material. In this work the ionization, dissociation and desorption
processes of pyrimidine ice, a nucleotide precursor molecule, were
experimentally studied applying the time-of-flight mass spectrometry
technique, in order to evaluate their destruction pathways in protoplanetary
disks. These processes were stimulated by soft X-rays from 397 to 430 eV
delivered by synchrotron light source. The photodesorption ion yield (ion
photon-1) of several ions such as HCN+, C4H2+,
HC3NH+, and C3H3N+ among other ionic fragments were
determined. Considering that TW Hydrae has an integrated X-ray luminosity
(LX) from 0.2 to 2 keV of ∼ 1 × 1030 erg s-1,
the ion flux (ion cm–2 s-1) desorbed from the grain surface and the
ion production rate (ion cm–3 s-1) were determined as a function of
the distance from the central star. The results show that ionic species are
formed from ice due to photons interaction, highlighting the role of the ice
chemistry in the molecular enrichment in protoplanetary disks. |
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