Interaction of Chiral Propylene Oxide (CH₃CHCH₂O) with Helium: Potential Energy Surface and Scattering Calculations

The first chiral interstellar organic molecule, propylene oxide (CH3CHCH2O), was detected recently toward the galactic center. Accurate determination of its abundance relies on the knowledge of collisional cross sections. We investigate here the rotational excitation of propylene oxide induced by collisions with helium. The calculations are based on a three-dimensional CH3CHCH2O–He potential energy surface computed using the explicitly correlated coupled-cluster theory extended to the complete basis set limit [CCSD­(T)-F12b/CBS]. The interaction energies are fitted using an interpolating moving least squares method, and this potential is refitted using a partial wave expansion based on spherical harmonics. Rotational cross sections are obtained at the quantum close-coupling level for a collision energy of 10 cm–1. Convergence issues and collisional propensity rules are discussed