Protonh 2 11/2 and octupole excitations in148Dy and149Dy

The yrast states of148Dy and149Dy have been studied by gamma-ray and conversion electron measurements in (agr, xn) and (16O,xn) reactions on enriched152Gd and135Ce targets. Level schemes to above 4 MeV for the two nuclei are reported. The pgrh 2 11/2 spectrum identified in148Dy and the pgrh 11/2 effective chargee eff=1.52±0.05e, derived from the measuredE2 transition rate between the (pgrh 2 11/2) 10+ and 8+ states, are discussed and compared with results for other two-particle nuclei. The yrast cascades in148Dy and149Dy continue above the (pgrh 2 11/2) 10+ and pgrh 2 11/2 vf 7/2) 27/2– states by sim 1 MeVE1 transitions de-exciting the lowest members of octupole multiplets built on these states. The energy shifts for the observed members of the pgrh 2 11/2 × 3– multiplet are analyzed in terms of twoparticle-phonon exchange coupling using an empirical coupling strength extracted from the one valence particle nucleus147Tb. The dominantvf 7/2×3– character of low-lying 13/2+ isomers in149Dy and otherN=83 nuclei is emphasized.