When dealing with quadrupole or magnetic splitting separately with chemical isomer shifts the recorded spectrum has uniform shifts of resonance lines with no change in their relative separations. However, both the quadrupolar and magnetic interactions depend upon angle and so when they are both present the interpretation of the spectrum can be complex.
The situation can be simplified a great deal if two assumptions are made
For most Fe spectra the result is a shift in the relative position of lines 1,6 with lines 2,3,4,5. For a positive quadrupole splitting lines 1,6 are shifted positively relative to lines 2,3,4,5 and vice versa. The line separations are equal when there is no quadrupole effect or when .
Dr John Bland, 15/03/2003