Theoretical study of the interaction of Fe, Fe+, and FeCO with Ar

Ab initio Hartree–Fock calculations were performed on FeAr and FeAr+ in order to determine the interaction of both neutral and singly‐ionized Fe atoms trapped in Ar, and on ArFeCO and FeCOAr in order to ascertain the effect of an Ar matrix on the FeCO molecule. Quadrupole splittings and isomer shifts are computed using ab initio orbital populations and charge densities scaled by a relativistic factor. Good agreement between calculated and experimental hyperfine parameters is found in each case. The interaction energy for Fe+–Ar has been computed by ab initio Hartree–Fock and effective‐core potential (ECP) methods. Both approaches yield a minimum between Fe+ and Ar at approximately 7.6 bohr.