Rovibrational energy transfer in the He-C₃ collision: Potential energy surface and bound states

We present a four-dimensional potential energy surface (PES) for the collision of C₃ with He. Ab initio calculations were carried out at the coupled-cluster level with single and double excitations and a perturbative treatment of triple excitations, using a quadruple-zeta basis set and mid-bond functions. The global minimum of the potential energy is found to be −26.9 cm⁻¹ and corresponds to an almost T-shaped structure of the van der Waals complex along with a slightly bent configuration of C₃. This PES is used to determine the rovibrational energy levels of the He-C₃ complex using the rigid monomer approximation (RMA) and the recently developed atom-rigid bender approach at the Close Coupling level (RB-CC). The calculated dissociation energies are −9.56 cm⁻¹ and −9.73 cm⁻¹, respectively at the RMA and RB-CC levels. This is the first theoretical prediction of the bound levels of the He-C₃ complex with the bending motion.