Collectivity and the role of two-proton and two-neutron excitations in 82Kr

Excited states in 82Kr have been studied in the reaction 80Se(α, 2n) by using in-beam γ-ray spectroscopy. Measurements of γγ coincidences, excitation functions, angular distributions and the linear polarization of the γ-rays have been carried out. All together, 38 levels have been identified up to I = 12 h and excitation energies up to 6 MeV. For 23 of these levels the mean lifetime could be determined by Doppler shift and the pulsed-beam γ-timing methods. Most of the levels could be grouped into collective bands according to measured B(E2) values. Two sequences, Isup(π) = 8+, 10+, 12+, are interpreted as rotation-aligned 2q,p. bands built up on gsub(9/2) protons and neutrons, respectively. Interaction matrix elements between these bands were deduced as V < or approx. 10 keV. Additional states, Isup(π) = (6+), 7+, 8+, indicate coexistence of rotation-aligned and deformation-aligned 2q.p. excitations. An odd-parity ΔI = 1 band is ascribed to proton excitations of the type gsub(9/2) x psub(3/2)/fsub(5/2). Several fast M1 transitions with B(M1) = 0.1-1 W.u. have been observed between states of equal spin. They are interpreted as being due to configuration mixing. (orig.)