How do complex organics and aromatic molecules form in cold clouds? · revision history

Revision 2

Accepted · core change · record

Changes against revision 1:

Title
How do complex organics and aromatic molecules form in cold clouds?
Plain
Radio telescopes have found large ring-shaped carbon molecules and other complex organics in a dark cloud only about 10 degrees above absolute zero. Chemistry models predict far smaller amounts than are seen.
Precise · changed · core
Revision 1: In TMC-1 (T ~ 10 K, n_H2 ~ 1e4 cm^-3) radio spectroscopy has detected complex organic molecules and cyano-substituted polycyclic aromatic hydrocarbons (cyanonaphthalenes, 2021; cyanopyrene, 2024; cyanocoronene, 2025) at abundances orders of magnitude above bottom-up gas-grain models. Identify the formation pathways (barrierless gas-phase growth, grain-surface chemistry with nonthermal desorption, or inheritance from an earlier phase) that reproduce the observed abundances.
Revision 2: In TMC-1 (T ~ 10 K, n_H2 $\sim 10^{4}$ cm^-3) radio spectroscopy has detected complex organic molecules and cyano-substituted polycyclic aromatic hydrocarbons (cyanonaphthalenes, 2021; cyanopyrene, 2024; cyanocoronene, 2025) at abundances orders of magnitude above bottom-up gas-grain models. Identify the formation pathways (barrierless gas-phase growth, grain-surface chemistry with nonthermal desorption, or inheritance from an earlier phase) that reproduce the observed abundances.
Settled by
A chemical network with laboratory-measured rate coefficients that reproduces the observed PAH and organic abundances in TMC-1 at its estimated age.
Kind
phenomenon
Answer type
mechanism
References
(empty)
Literature status
open
Status note
(empty)
Posed since
2021

Decisions