Isotopic shift in the3P1-3P0 Mg transition

High precision frequency measurements of the3P1-3P0 transitions have been performed for the three natural abundant Mg-isotopes in a metastable atomic beam. A second order hyperfine theory for two-electron atoms allows the determination of the centre-of-gravity for25Mg and then the evaluation of the isotopic shift displacements. The high resolution frequency measurements (10−8) show a noticeable departure of the total shift from a linear dependence with respect to the atomic mass.