isotope shift

Isotope shift

A small difference between the different isotopes of an element in the transition energies corresponding to a given spectral line transition. For a spectral line transition between two energy levels a and b in an atom or ion with atomic number Z, the small difference ΔEab = Eab(A) - Eab(A) in the transition energy between isotopes with mass numbers A, and A is the isotope shift. It consists largely of the sum of two contributions, the mass shift (MS) and the field shift, also called the volume shift. The mass shift is customarily divided into a normal mass shift and a specific mass shift; each is proportional to the fractional mass difference (A - A)/AA. The normal mass shift is a reduced mass correction that is easily calculated for all transitions. The specific mass shift is produced by the correlated motion of different pairs of atomic electrons and is, therefore, absent in one-electron systems. The field shift is produced by the change in the finite size and shape of the nuclear charge distribution when neutrons are added to the nucleus. See Atomic structure and spectra, Nuclear structure

isotope shift

[′ī·sə‚tōp ‚shift]
(spectroscopy)
A displacement in the spectral lines due to the different isotopes of an element.
References in periodicals archive ?
The isotope shift, particularly, is one of the dominant factors in achieving isotopic selectivity and is required to be optimized for each excitation transition by identification.
where [[GAMMA].sub.nat] is the homogeneous natural linewidth and [DELTA]v is the isotope shift of the specific transition.
They showed that the optical selectivity of Sr-90 of the scheme is around [10.sup.6]; however, the linewidth of the third-step transition of 487 nm is so large that the isotope shift cannot be evaluated [16].
Caption: Figure 4: Isotope shift of strontium for the 393.8 nm transition.
But lvany and Salawitch say that event can account for only part of the isotope shift. To explain the rest, they propose that wildfires burned 25 percent of the vegetation on land, filling the air with isotopically light carbon that dissolved into the ocean.
Lower down, including the Minija-Jura boundary interval, the [[delta].sup.13]C curve is variable but low-level plateau-like in the named west Lithuanian core sections, making it impossible to identify any small variation that could be connected with an oxygen isotope shift.
The results reveal close agreement between the experimental and computed values of helium's so-called isotope shift.
A novel procedure allowed them to measure the wavelength difference, or isotope shift, between helium-3 and helium-4 without having to measure the exact wavelength corresponding to each transition.
Three global carbon isotope shifts in the Silurian of Podolia (Ukraine): stratigraphical implications.
The isotope shifts suggest the water in this area cooled by 3[degrees]C or became less salty, or both.