Laserspectroscopic investigations were performed on a collimated atomic beam of barium (natural isotope abundance). The metastable ground levels (D and D ) of the investigated lines were populated by a discharge burning in barium vapour directly in front of the oven hole. We could investigate 14 spectral lines between 580 and 690 nm. The tensor polarizabilities of the upper and the lower level as well as the differences in the scalar polarizabilities could be determined. Spectra in magnetic fields up to 0.03 Tesla showed no deviation from the pattern resulting from a simple Russell-Sounders coupling.

Compared to the Neon atom, where levels belonging to different level groups nl or nl' are well separated from each other, most of the level groups in the neutral xenon atom overlap. We present investigations of the groups 7p, 6p' and 6d and discuss the effects of the overlapped arrangement of the levels to the magnitude and direction of the Stark shifts. From the measured dependency from the electric field strength, we have determined cuefficients which allow the calculation of the Stark shift for arbitrary field strengths.