Further evidence on shape coexistence in As-72

The As-72 nucleus was studied via the (alpha,n gamma) reaction at 14.2 MeV bombarding energy, Single gamma-, gamma gamma-coincidence, and internal con version electron spectra were measured with Ge(HP) gamma-ray and supercondu cting magnetic lens plus Si(Li) electron spectrometers. On the basis of the internal conversion coefficients of As-72, transitions, parities of the me dium-spin levels up to 1.4 MeV excitation energy were determined, resulting in unambiguous parities also for the heads of the bands observed previousl y. The states observed were assigned to proton-neutron multiplets on the ba sis of their decay properties. The energy splittings of the observed multip lets are in accordance with the prediction of the previous interacting boso n-fermion-fermion model (IBFFM) calculations using a transitional core lyin g between the vibrational SU(5) and gamma-soft O(6) limits, except that of the pi g(9/2)vg(9/2) multiplet, which was described using the deformed SU(3 ) core in the present IBFFM calculations. Such a core structure is in accor dance with previous particle-rotor and Hartree-Fock-Bogoliubov calculations . [S0556-2813(99)03903-5].