Rotational (de)-excitation of linear C3O by collision with H2

Abstract Tricarbon monoxide (C3O) is a linear carbon chain molecule, detected in the interstellar medium (ISM), that plays a crucial role in the formation of complex organic molecules. Despite numerous spectroscopic and theoretical studies, detailed dynamic investigations of C3O’s formation and stability in the ISM are lacking. This study focuses on the collisional behavior of C3O with H2, the main constituent of the ISM, through quantum-mechanical calculations of the rotational excitation and de-excitation cross sections. The geometry optimization of C3O was performed using state-of-the-art computational methods, with the CCSD(T)-F12a/aug-cc-pVTZ level of theory. The potential energy surface (PES) of the C3O–H2 system was determined by treating both molecules as rigid rotors and describing their interaction geometry using Jacobi coordinates. The PES was sampled for five specific H2 orientations, and the positions and depths of the interaction potential wells were analyzed. The close-coupling dynamical scattering calculations were performed, for energies up to 1000 cm−1, by our primary in-house code called Yumi. These calculations were carried out for the first 41 rotational levels of C3O with the first three excited states of H2. The (de)-excitation rotational rate coefficients were then derived form a Maxwell Boltzmann average of cross sections over kinetic energies for temperatures up to 150 K. The results provide novel collision data for the C3O–H2 system, offering a more complete and physically relevant framework for astrochemical simulations and an accurate analysis of astrophysical data.