  Aluminium monofluoride (AlF) is a promising candidate for laser cooling and
the production of dense ultracold molecular gases, thanks to its relatively
high chemical stability and diagonal Frank-Condon factors. In this study, we
examine the interactions and collisions of AlF in its $X^1\Sigma^+$, $a^3\Pi$,
and $A^{1}\Pi$ electronic states with ground-state He using state-of-the-art
\textit{ab initio} quantum chemistry techniques. We construct accurate
potential energy surfaces (PESs) employing either the explicitly correlated
coupled-cluster CCSD(T)-F12 method augmented by the CCSDT correction or the
multireference configuration-interaction method for higher-excited electronic
states. Subsequently, we employ these PESs in coupled-channel calculations to
determine the scattering cross-sections for AlF+He collisions and bound states
of the complex. We estimate the uncertainty of the calculated PESs and apply it
to assess the uncertainty of the scattering results. We find a relatively low
sensitivity of the cross-sections to the variation of the PESs, but the
positions of shape resonances remain uncertain. The present results are
relevant for further improvements and optimizations of buffer-gas cooling of
AlF molecules.
