English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Methane is typically thought to be formed in the solid state on the surfaceof cold interstellar icy grain mantles via the successive atomic hydrogenationof a carbon atom. In the current work we investigate the potential role ofmolecular hydrogen in the CH$_4$ reaction network. We make use of an ultra-highvacuum cryogenic setup combining an atomic carbon atom beam and both atomicand/or molecular beams of hydrogen and deuterium on a H$_2$O ice. Theseexperiments lead to the formation of methane isotopologues detected in situthrough reflection absorption infrared spectroscopy. Most notably, CH$_4$ isformed in an experiment combining C atoms with H$_2$ on amorphous solid water,albeit slower than in experiments with H atoms present. Furthermore,CH$_2$D$_2$ is detected in an experiment of C atoms with H$_2$ and D$_2$ onH$_2$O ice. CD$_4$, however, is only formed when D atoms are present in theexperiment. These findings have been rationalized by means of computationalchemical insights. This leads to the following conclusions: a) the reaction C +H$_2$ -> CH$_2$ can take place, although not barrierless in the presence ofwater, b) the reaction CH + H$_2$ -> CH$_3$ is barrierless, but has not yetbeen included in astrochemical models, c) the reactions CH$_2$ + H$_2$ ->CH$_3$ + H and CH$_3$ + H$_2$ -> CH$_4$ + H can take place only via a tunnelingmechanism and d) molecular hydrogen possibly plays a more important role in thesolid-state formation of methane than assumed so far.

Methane formation in cold regions from carbon atoms and molecular hydrogen