Testing Physics Beyond the Standard Model by using Isotope Shift Spectroscopy*

Isotope's are atom's of the same atomic number but differ in the number of neutrons. This change primarily brings about two major changes in the atom: 1) with the introduction of additional neutrons there is an increase in the nuclear mass which changes the kinetics of the nucleus about the center of mass of the atom. 2) This addition of neutron changes the nuclear charge distribution, affecting how the electrons feel the effects of the nucleus. Both of these changes bring about a change in the atomic energy levels. And this change in the energy levels is what is referred to as Isotope Shift.

Researchers all over the world have been looking for new particle's beyond the current accepted standard model of fundamental interactions in physics. Such research is most famously carried out at the Large Hadron Collider. On the contrary isotope shift studies are less resource intensive and provides very accurate results.

Isotope shift can be thought of as comprising of Mass Shift which is caused by the motion of the nucleus about the center of mass of the atom and Field Shift which arises due to the change of the nuclear charge radius between isotopes.

One of the tools to study Isotope shift was developed by W.H. King called as the Kings plot analysis which looks at various transition frequencies between different isotopes pairs. The Kings relation holds accurately in the first order approximation and so therefore any deviation from linearity observed in the plot can be associated to the New Physics. Which is supposedly due to the predicted spin-less scalar boson which interacts between the neutrons and electrons via the Yukawa Potential. 

With the use of even more fancier method's like Generalised Kings Plot, one can analyse Isotope Shift with less restrictions posed by experiemental uncertainities arising from lack of knowledge of nuclear masses and nuclear radii.

Field Shift and Mass Shift's were calculated for a wide range of Hydrogen like atoms and the results were consistent with the theory. Also Non-Linearity in the Kings Plot was calculated and compared using different methods. 

Note: Hydrogen like Systems with no nuclear spin were considered in the analysis as Hyperfine structure generated due to nuclear spin is a known source of King plot Non-Linearity.