Einstein predicts two types of time dilation, both of which have been tested and confirmed. One is…
What should be noted is that the deuterium spectrum comes out at about 2 angstrom towards the blue end of the spectrum as compared to hydrogen.
Heavy isotopes emit bluer light than lighter ones
It follows from this that an increase in mass of atomic nuclei will shift the light spectrum of the affected matter towards the blue end of the spectrum.
Note that the exact energy levels of the electrons are determined by the size of the nucleus. This lends support to the bouncing electron model in that such a model provides a mechanism for the electron to be affected by the size as well as the charge of the nucleus.
A bigger nucleus will act as a bigger trampoline for the electrons, leading to more energetic bounces despite the fact that the charges involved are unchanged.