Quantum study of the rovibrational relaxation of HF by collision with 4 He on a new potential energy surface.

The HF molecule is considered the main reservoir of fluorine in the interstellar medium (ISM). Also, the interactions of this molecule with the most common atoms and molecules in the ISM have attracted great interest from the astrochemical community. Collisions between HF and helium have recently caused controversy following a study using a two-dimensional SAPT potential energy surface (PES) that exhibited large discrepancies with previous scattering calculations based on more recent ab initio potentials. To address this issue, our current work aims to develop the most precise three-dimensional PES for the HF+He system. We employ the size-consistent CCSD(T) method in conjunction with the aug-cc-pV6Z basis set. The main features of the new PES as well as the bound states of the He-HF complex are compared to the existing data. The new PES is then utilised to conduct close coupling calculations that demonstrate He-HF as a good instance of vibration-rotation near resonant energy transfer. The novel rate coefficients will be accessible via the BASECOL database, and the use of the new PES is advised when describing HF in helium droplets.