Molecular-Orbital Study of Mössbauer Results on Iron Dissolved in Solid Noble Gases

Molecular-orbital calculations on the iron dimer are combined with Mössbauer data on monomeric and dimeric iron dissolved in solid noble gases to suggest for the dimer an Fe-Fe separation somewhat over 3.99 Å, to indicate for ${}_{}{}^{57m}{}_{}{}^{}\mathrm{Fe}$ a nuclear quadrupole moment of +0.20±0.03 b, and to support the choices of $9.1{a_0}^{-3\mathrm{}}$ and $6.7{a_0}^{-3\mathrm{}}$ for the electron densities produced at the nucleus of an iron atom by a pair of $4s$ electrons in configuration $3d^6 4s^2$ and by a single $4s$ electron in configuration $3d^6 4s$, respectively.