Isotope Shift Spectroscopy. A displacement or splitting of spectral lines indicating the presence of isotopes of an element. Isotope shifts are caused by two different phenomenon. The first one is the Mass Shift (MS). The second one is the Field Shift (FS). In the lighter nuclei the MS is the dominant shift that takes place, this is due to the finite mass of the nuclei. In the heavier nuclei, the FS is dominant, this is because of the none zero nuclear volume. It is the field shift, which provides information on the radial parameters of the nucleus and is therefore the part of interest in nuclear physics. However the mass shift must be considered as it is necessary to be able to allow for its effect in determining the field shift. The FS is due to the change in the spatial distribution of the nuclear charge between isotopes while the MS is due to the change in kinetic energy of the nucleus, which in turn depends on the nuclear mass. The MS can be further divided into the sum of the normal mass shift (NMS) and specific mass shift (SMS). The NMS is due to the difference in the reduced mass of the electron-nucleus system and is readily calculated. The SMS is due to momentum correlations among electrons and is not readily calculated. The presence of the SMS prevents the extraction of the FS from measured isotope shifts.
The technology of isotope shift covers many fields in chemistry, physics, biology and even semiconductor technology. The main instrument used in finding isotope shifts is the Spectroscope, this is an instrument that breaks up a beam of light or other electromagnetic wave into the various colors or wavelengths which are present, allows measurement of the wavelengths of the various components, and sometimes allows measurement of the relative intensity of these components. For visible light, the light is normally broken up or dispersed with either a strong prism or a diffraction grating. There are many experiments that have been done using isotope shift technology, one of the main ones would be to see the isotope shift in the spectra of hydrogen and deuterium, another interesting effect would be isotope effects in sonoluminescene.It is now known that most elements in nature consists of two or more isotopes with the exception of beryllium,aluminum, phosphorus and sodium. The latest research being done using isotope shift is as various as the subject itself, to learn more about the subject, books on isotope shifts for further reading is availabe.