Application of closed-orbit theory to barium scaled-energy Stark spectra

High-resolution scaled-energy spectra of barium Rydberg atoms in a static e lectric field are studied. Starting from the 6s5d(3)D3 metastable state we investigate Rydberg series converging to the 6s(1/2) ionization limit. Spec tra at scaled energies epsilon = -2.94, -2.35 and -1.76 are recorded and Fo urier transformed. Hydrogenic closed-orbit theory, including recent m(l) = 0 corrections for actions around a bifurcation, reproduces the positions of the peaks but does not reproduce the intensities. A recent extension of cl osed-orbit theory, incorporating core scattering for nonhydrogenic atoms, i s applied. In spite of the success of this technique in analysing scaled-en ergy spectra for light atoms with one (small) quantum defect the measured i ntensities in the barium case cannot be reproduced with this method.