Hi Sanele:

Mossbauer spectroscopy uses the presence of nuclear resonances in a sample and measures the energy positions of these resonances with respect to the energy of the Mossbauer source. The electronic environment of the resonant nuclei, for example 57Fe, determines the position of those resonances. The isomer shift is the difference between the emission energy of the source and the absorption energy of the sample. If there are many lines the center average of all lines need to be used. Depending on the particular sample/source combination the isomer shift can be positive or negative. Isomer shift are always given with respect to a reference material which in publications is often chosen to be iron metal at ambient conditions. In your publications, it therefor important to mention the reference when you give isomer shifts.

Example:  Your source is 57Co(Rh), and you measure an isomer shift of 1 mm/s. The isomer shift of an iron foil at ambient conditions measured with same source is -0.1 mm/s. Therefore the isomer shift of your sample relative to the iron foil reference is 1.1 mm/s.

 Hi Wolfgang Sturhahn,

Thank you for your assistance really appreciate it.