Isomeric shift

Isomeric shift (or isotopic shift) is a phenomenon observed in nuclear magnetic resonance (NMR), particularly in the context of Mössbauer spectroscopy. It refers to the change in energy of gamma rays emitted or absorbed by a nucleus when it is in a different chemical or physical environment compared to a reference state. In the case of Mössbauer spectroscopy, the isomeric shift is primarily influenced by the electronic environment surrounding the nucleus, particularly the s-electron density at the nucleus.