Efficient stabilization of cyanonaphthalene by fast radiative cooling and implications for the resilience of small PAHs in interstellar clouds.
Mark H StockettJames N BullHenrik CederquistSuvasthika IndrajithMingChao JiJosé E Navarro NavarreteHenning T SchmidtHenning ZettergrenBoxing ZhuPublished in: Nature communications (2023)
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.
Keyphrases
- polycyclic aromatic hydrocarbons
- convolutional neural network
- deep learning
- single molecule
- electron transfer
- energy transfer
- heavy metals
- antibiotic resistance genes
- climate change
- lymph node metastasis
- machine learning
- squamous cell carcinoma
- room temperature
- microbial community
- depressive symptoms
- neural network
- monte carlo