SE841: A potential path for the formation of PAHs in deep interstellar space: Exploration of the indenyl and benzyl radical reaction

The potential energy surfaces (PESs) were explored for the radical reaction of indenyl (C9H7) with benzyl (C7H7) which possibly lead to C16H10 isomers including acephenanthrylene, fluoranthene, indeno(2,1-a)indene, and pyrene. These represent polycyclic aromatic hydrocarbons (PAH) which are produced on Earth through incomplete combustion of fossil fuels and also have been found to exist in the interstellar medium and on carbonaceous asteroids such as 101955 Bennu. PAHs, including pyrene, fluoranthene, and phenanthrene have been detected in returned samples from the OSIRIS-REx mission to 101955 Bennu. In this work we explored their possible formation pathways. The fundamental understanding of the key processes in the synthesis of PAHs provide critical insights into how complex aromatic structures, graphenes, fullerenes, and carbonaceous nanoparticles (soot, interstellar grains) are formed. Achieving this knowledge represents a critical step in the development of clean combustion technologies and in reducing environmental pollution, as well as, in our comprehension of the chemical evolution in the universe. For geometry optimization and calculations of vibrational frequencies, wB97XD functional was used with conjunction of the 6-311G** basis set; CCSD(T) and second order Moller-Plesset set perturbation theory (MP2) calculations were used refine single point energies. Product branching ratios and rate constants were calculated using the RRKM Master Equation approach. The theoretical analysis allowed us to predict the reaction outcome under various conditions.