Abstract. Using the atomic beam magnetic resonance method, the five hyperfine structure separations in the 4f 3 6s 2 419. 2 ground state of 141 _ 59P1 have been measured. The results are:6477.913423 (17) 6 5 5556.359848 (6) 5 4 4633.023306 (2) 4 3 3708.201146 (5) 3 2 2782.190601 (15) From these quantities, the multipole interaction constants Ak, k = 1, 2, 3, 4 between the nucleus and the electron shell have been calculated. A 4 especially then served to give the following limit for the intrinsic hexadecapole moment: IQ4ol <0.4eb 2. Furthermore, the gs-factors of the 41 multiplet have been measured at magnetic fields of 300 Oe. The results are: gj(419.2) =0.731 037 1(15) gj(4Ii1~2) =0.965 1476 (20) gj(41132) = 1.106 319 7(40) gj(d'I152)= 1.197963 (30) Small corrections due to perturbations by neighbouring fine structure levels are included.

Using the atomic beam magnetic resonance method, precision measurements of the hyperfine structure and Zeeman interactions have been performed in the ground state 4f 126s 2 3H 6 of 167Er. The experimental data were analyzed using an effective operator parametrized in the space of states of the ground state multiplet. It yielded eight effective hyperfine structure and Zeeman interaction constants which served to calculate the seven hyperfine separations of the ground state. The results are: 2F2F ' vvp, (MHz)

Using the atomic beam magnetic resonance method we observed Ramsey patterns of strongly field dependent transitions of Li, Na and Rb at high magnetic fields. The structures were of high symmetry, with half widths of the central minimums between 20 kHz and 6 kHz. In a first experiment we determined the g j-factor ratio gj(~ = 1 + 3(70). I0-" o.