Hydrogen isotope fractionation in methane plasma

作者：Robert Francois^*; Derenne Sylvie; Lombardi Guillaume; Hassouni Khaled; Michau Armelle; Reinhardt Peter; Duhamel Remi; Gonzalez Adriana; Biron Kasia

来源：Proceedings of the National Academy of Sciences of the United States of America, 2017, 114(5): 870-874.

DOI：10.1073/pnas.1615767114

• hydrogen isotopes
• meteorites
• cosmochemistry
• methane plasma
• insoluble organic matter

The hydrogen isotope ratio (D/H) is commonly used to reconstruct the chemical processes at the origin of water and organic compounds in the early solar system. On the one hand, the large enrichments in deuterium of the insoluble organic matter (IOM) isolated from the carbonaceous meteorites are interpreted as a heritage of the interstellar medium or resulting from ion-molecule reactions taking place in the diffuse part of the protosolar nebula. On the other hand, the molecular structure of this IOM suggests that organic radicals have played a central role in a gas-phase organosynthesis. So as to reproduce this type of chemistry between organic radicals, experiments based on a microwave plasma of CH4 have been performed. They yielded a black organic residue in which ion microprobe analyses revealed hydrogen isotopic anomalies at a sub-micrometric spatial resolution. They likely reflect differences in the D/H ratios between the various CHx radicals whose polymerization is at the origin of the IOM. These isotopic heterogeneities, usually referred to as hot and cold spots, are commensurable with those observed in meteorite IOM. As a consequence, the appearance of organic radicals in the ionized regions of the disk surrounding the Sun during its formation may have triggered the formation of organic compounds.

• 出版日期2017-1-31