Experimental and theoretical investigation of the isotope shift of the 4D level in atomic potassium

Abstract

Doppler-free two-photon laser spectroscopic measurements in the deep red spectral region have been performed on the transition 42Sx/z---~42Dj in the naturally abundant isotopes 39 and 41 of atomic potassium. The 4D level isotope shift, -81 _+ 12 MHz was obtained by combining the current results with data from Rydberg-state spectroscopy. Many-body perturbation theoretical calculations of the specific mass shift in the measured state are also presented. With the use of Brueckner orbitals the value -70 MHz was obtained in substantial agreement with the experimental result.