Isotopic shift
Encyclopedia
The isotopic shift is the shift in atomic spectra which occurs when one nuclear isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...

 is replaced by another. If the spectra have also hyperfine structure
Hyperfine structure
The term hyperfine structure refers to a collection of different effects leading to small shifts and splittings in the energy levels of atoms, molecules and ions. The name is a reference to the fine structure which results from the interaction between the magnetic moments associated with electron...

the shift refers to the center of gravity of the spectra. There are two effects which contribute to this shift:
  • The mass difference. This difference induces a change in the reduced electronic mass. This purely kinematical effect, studied theoretically by Hughes and Eckart is important for light elements.

  • The volume difference. This difference induces a change in the electric charge distribution of the nucleus. This effect is important in heavy elements and its first theory was formulated by Pauli and Peierls.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK