γ-ray spectroscopy of excited states in 143Eu

The level structure of the N=80 nucleus 143Eu has been studied by the 144Sm(p,2nγ)143Eu reaction using a 30-MeV p beam. We have assigned 37 γ rays deexciting 30 states in 143Eu, placed on the basis of excitation functions and γ-γ coincidence information. Angular distributions were taken at 900, 1000, 1100, 1250, 1400, and 1550 with respect to the beam direction, yielding the A2 and A4 coefficients. The in-beam experiments tended to excite higher-spin states than those known from existing β-decay data. Taking the various data together, we could make definite J/sup π/ assignments for most of the states in 143Eu. Calculations were performed to explain the resulting level structure in terms of a triaxial weak-coupling model for both prolate and oblate deformations. These calculations indicate that 143Eu has a slight oblate deformation