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 Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Interstellar carbonaceous dust is mainly formed in the innermost regions ofcircumstellar envelopes around carbon-rich asymptotic giant branch (AGB) stars.In these highly chemically stratified regions, atomic and diatomic carbon,along with acetylene are the most abundant species after H$_2$ and CO. In aprevious study, we addressed the chemistry of carbon (C and C$_2$) with H$_2$showing that acetylene and aliphatic species form efficiently in the dustformation region of carbon-rich AGBs whereas aromatics do not. Still, acetyleneis known to be a key ingredient in the formation of linear polyacetylenicchains, benzene and polycyclic aromatic hydrocarbons (PAHs), as shown byprevious experiments. However, these experiments have not considered thechemistry of carbon (C and C$_2$) with C$_2$H$_2$.  In this work, by employing a sufficient amount of acetylene, we investigateits gas-phase interaction with atomic and diatomic carbon. We show that thechemistry involved produces linear polyacetylenic chains, benzene and otherPAHs, which are observed with high abundances in the early evolutionary phaseof planetary nebulae. More importantly, we have found a non-negligible amountof pure and hydrogenated carbon clusters as well as aromatics with aliphaticsubstitutions, both being a direct consequence of the addition of atomiccarbon. The incorporation of alkyl substituents into aromatics can berationalized by a mechanism involving hydrogen abstraction followed by methyladdition. All the species detected in gas phase are incorporated into thenanometric sized dust analogues, which consist of a complex mixture of sp,sp$^2$ and sp$^3$ hydrocarbons with amorphous morphology.

The chemistry of cosmic dust analogues from C, C$_2$, and C$_2$H$_2$ in C-rich circumstellar envelopes