Quasiparticle-excitations in light even-even barium nuclei

The nucleus 126Ba was investigated by inbeam gamma-ray spectroscopy using the 116Sn(13C,3n)126Ba reaction. γ-singles spectra, γ-angular distributions, γ-excitation functions and γγ-coincidences were measured, partially by the use of anticompton techniques. 54 excited states were established and 83 γ-lines were placed into the level scheme of 126Ba. Several spin and parity assignments were made. More than 14 mean lifetimes of excited states in 126Ba were determined by an RDDS-measurement. Here the 100Mo(30Si,4n)126Ba reaction was used in order to populate excited states of 126Ba. The experimental Routhians of the observed bands are analyzed with the symmetric Cranked Shell Model (CSM). In addition 2-quasiparticle Routhians are constructed from the single particle configurations of the neighbouring odd nuclei of 126Ba, 128Ba and 130Ba and were then compared with the negative parity bands of the even-even nuclei. Both analysis show the h11/2g7/2-neutron character of the strongly coupled bands and the 2-quasi-proton character of the more decoupled band structures. The mean residual interaction could be determined to be about -200 keV to -300 keV for the neutron bands and between -300 keV and -550 keV for the proton bands in the Barium nuclei. (orig./HSI)