Fine structures of thendD2andnfF2sequences in singly ionized beryllium

Abstract
Fine structures in the ndD2, n=4,5 and nfF2, n=4,5,6 levels in Be ii have been measured, using fast-beam, level-crossing spectroscopy. The results, accurate to within 103, point to small deviations from a hydrogenic fine-structure splitting due to correlation effects involving the 1s2 core for the nfF2 levels.