[en] Earlier Moessbauer effect experiments on ⁵⁷Co diffused in Al show two different positions for the Co-atoms after irradiation of the sample with fast neutrons: substitutional Co and interstitial Co. In order to study the landing dynamics of Co in Al we have implanted ⁵⁷Co in Al at 4.2⁰K, at which temperature the Al-interstitials are still immobile. The total implanted dose was 10¹⁴ at/cm², the implantation energy 85 keV. The Moessbauer spectrum shows one line corresponds to substantial Co-atoms, the other one comes from interstitial Co-atoms (in the <100> Co--Al mixed dumbbell position). The population of the substitutional site, found to be 0.46 +- 0.02, can give information on the interaction potentials between Co--Al and Al--Al when the results are interpreted on the basis of a replacement collision model modified by taking into account a spontaneous trapping volume for the lattice atom recoil, around substitutional Co