Efficient stabilization of cyanonaphthalene by fast radiative cooling and implications for the resilience of small PAHs in interstellar clouds.

Autor: Stockett MH; Department of Physics, Stockholm University, Stockholm, Sweden. Mark.Stockett@fysik.su.se., Bull JN; School of Chemistry, University of East Anglia, Norwich, United Kingdom., Cederquist H; Department of Physics, Stockholm University, Stockholm, Sweden., Indrajith S; Department of Physics, Stockholm University, Stockholm, Sweden., Ji M; Department of Physics, Stockholm University, Stockholm, Sweden., Navarro Navarrete JE; Department of Physics, Stockholm University, Stockholm, Sweden., Schmidt HT; Department of Physics, Stockholm University, Stockholm, Sweden., Zettergren H; Department of Physics, Stockholm University, Stockholm, Sweden., Zhu B; Department of Physics, Stockholm University, Stockholm, Sweden.
Jazyk: angličtina
Zdroj: Nature communications [Nat Commun] 2023 Jan 24; Vol. 14 (1), pp. 395. Date of Electronic Publication: 2023 Jan 24.
DOI: 10.1038/s41467-023-36092-0
Abstrakt: After decades of searching, astronomers have recently identified specific Polycyclic Aromatic Hydrocarbons (PAHs) in space. Remarkably, the observed abundance of cyanonaphthalene (CNN, C 10 H 7 CN) in the Taurus Molecular Cloud (TMC-1) is six orders of magnitude higher than expected from astrophysical modeling. Here, we report unimolecular dissociation and radiative cooling rate coefficients of the 1-CNN isomer in its cationic form. These results are based on measurements of the time-dependent neutral product emission rate and kinetic energy release distributions produced from an ensemble of internally excited 1-CNN + studied in an environment similar to that in interstellar clouds. We find that Recurrent Fluorescence - radiative relaxation via thermally populated electronic excited states - efficiently stabilizes 1-CNN + , owing to a large enhancement of the electronic transition probability by vibronic coupling. Our results help explain the anomalous abundance of CNN in TMC-1 and challenge the widely accepted picture of rapid destruction of small PAHs in space.
(© 2023. The Author(s).)
Databáze: MEDLINE
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