Hyperfine-structure investigation in the 6s5d configuration of 135Ba and 137Ba

The hyperfine structure of the metastable states of the 6s5d configuration of 135Ba and 137Ba has been studied by the atomic-beam magnetic resonance (ABMR)method. The metastable barium states were populated in a plasma-discharge inside the atomic-beam oven. The atoms emerging from the ABMR-apparatus were detected by the use of a dye-laser. Compared to conventional methods this technique has the advantage of being state selective. The following magnetic dipole and electric quadrupole interaction constants a and b have been obtained: 137Ba: a(3D1)= -520.536 (3) MHz, b(3D1)= 17.890 (3) MHz, a(3D2)= 415.928 (3) MHz, b(3D2)= 25.899 (13) MHz, a(3D3)= 456.559 (4) MHz, b(3D3)= 47.390 (16) MHz. 135Ba: a(3D1)= -465.166 (4) MHz, b(3D1)= 11.642 (4) MHz, a(3D2)= 371.736 (4) MHz, b(3D2)= 16.745 (14) MHz, a(3D3)= 408.038 (6) MHz, b(3D3)= 30.801 (24) MHz. Using these constants and the earlier known ones for the 1D2 state the hyperfine structure for the 6s5d configuration has been analyzed with an effective hyperfine hamiltonian. Hyperfine parameters obtained from the analysis have been compared with theoretical values calculated with relativistic self-consistent-field (SCF) wavefunctions. The quadrupole moments have been evaluated with the following result Q(135Ba)= 0.20(3) b and Q(137Ba)= 0.34(4) b uncorrected for the quadrupole shielding. (orig.)