Highly correlated electronic structure calculations of the He-C₃ van der Waals complex and collision-induced rotational transitions of C ₃

An accurate 2D ab initio potential energy surface of the He-C₃ collisional system is calculated using the supermolecular coupled-cluster method with up to perturbative quadruple excitations, CCSDT(Q). This interaction potential is then incorporated in full close-coupling calculations of rotational excitation/de-excitation cross sections in He + C₃ collisions for rotational levels j = 0, 2,..., 10 and collision energies up to 1000 cm ^-1. Corresponding rate coefficients are reported for temperature between 1 and 100 K. Results are found to be in excellent agreement with available theoretical data that were restricted to the temperature range of 5-15 K. Implications of the computed rate coefficients to astrophysical models of C₃ and carbon clusters in interstellar and circumstellar environments are discussed.