Can third-body stabilisation of bimolecular collision complexes in cold molecular clouds happen?

Abstract

For more than half a century, networks of radiative association, dissociative recombination, and bimolecular reactions have been postulated to drive the low-temperature chemistry of cold molecular clouds. Third-body stabilizations of collision complexes have been assumed to be ‘irrelevant’ due to short lifetime of such complexes. Here, we conduct crossed molecular beam studies of ground state atomic silicon with diacetylene in combination with electronic structure calculations and microcanonical kinetics models operating under cold molecular cloud conditions. Our combined experimental, electronic structure, and microcanonical kinetics modelling investigations provide compelling evidence that three-body collisions of molecular hydrogen with long-lived reaction intermediates accessed through intersystem crossing are prevalent deep inside molecular clouds. This concept might be exportable to reactions involving polycyclic aromatic hydrocarbons thus affording a versatile machinery to complex organics via third-body stabilizations of bimolecular collision complexes deep inside cold molecular clouds.

GRAPHICAL ABSTRACT

KEYWORDS:

• Third-body collisions
• silicon-carbon bond
• reaction dynamics
• astrochemistry

Acknowledgements

The authors thank Prof. Eric Herbst, University of Virginia, and Dr. Stephen J. Klippenstein, Sandia National Laboratories, for valuable discussions. AWJ gratefully acknowledges computing resources provided by Bebop, a high-performance computing cluster operated by the Laboratory Computing Resource Center at Argonne National Laboratory.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work at the University of Hawaii was supported by the U.S. National Science Foundation (CHE-1853541). BRLG acknowledges financial support from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, grant number 311508/2021-9) and CEFET-MG. AWJ was supported by the U. S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences through Argonne National Laboratory. Argonne is a U. S. Department of Energy laboratory managed by UChicago Argonne, LLC, under Contract Number DE-AC02-06CH11357.