Description of the neutron deficient Sr and Zr isotopes in the interacting boson model

Abstract

The available experimental data for the neutron deficient isotopes of Sr (78 to 86) and Zr (80 to 86) are collected and compared to the predictions of IBA-1 model calculations. The variations of the collectivity along these two isotopic chains is well reproduced with a set of smoothly varying parameters of the model. The description of both the energy levels and the B(E2) transition probabilities improves with decreasing N, the hamiltonian evolving towards an SU(3) dynamical symmetry. Both the large B(E2) value of the 2 1 + → 0 g.s. + transition and the predicted prolate shape for the very light isotopes, agree well with the recent findings of superdeformed nuclei around Z, N ≈ 38. Transition strengths for the (p, t) reaction are calculated and compared to experimental observations for 0 + states, and a discussion is made about the possible intruder character of the 0 2 + state. The interacting boson-fermion approximation (IBFA) model is used to extend the calculations to some odd nuclei. Two shell (1g 9 2 , 2d 5 2 ) calculations are performed for the positive-parity states in 83Sr, 81Sr and 85Y and they compare well with the experimental level scheme of these nuclei below 3 MeV excitation.