Interpretation of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">Fe</mml:mi></mml:mrow><mml:mrow><mml:mn>57</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>Isomer Shift

S>A study was made of the Mossbauer effect of Fe/sup 57/ in diand tri- vaient iron compounds and d-group metals. The Hartree-Fock calculations of Watson on the various 3d configurstions of iron were combined with the data on the isomeric shifts in the most ionic compounds to calibrate the shift in terms of s-electron density. The difference of the excited and ground state charge radii is calculated to be delta A/R = 1.8 x 10/sup -3/, with the effective radius of the ground state larger than that of the excited state. It is concluded that the ground state is probably not a simple shell state and that a general charge distribution accompanies the isomeric transition. (D.L.C.)