Nonyrast states of ¹⁰⁸Cd: Investigation with complementary γγ-spectroscopic methods

We investigated ¹⁰⁸Cd using a powerful combination of complementary γγ spectroscopic methods. Excited states were populated in the β decay of ¹⁰⁸In and with the ¹⁰⁵Pd(α,n) fusion-evaporation reaction near the Coulomb barrier. From γγ angular correlation analyses we found dominant M1 character for decays of three 2⁺ states between 2.1 and 2.65 MeV, indicating that the fundamental isovector quadrupole excitation in the valence shell, the so-called 2_ms⁺ state, is fragmented in ¹⁰⁸Cd. Effective lifetimes from the Doppler-shift attenuation method (DSAM) provided lower limits for the absolute transition strengths of the interesting decays. Our findings on mixed-symmetry 2⁺ states were compared to the neighboring nucleus ¹¹²Cd and IBM-2 predictions in the vicinity of the pure U(5) and O(6) dynamical symmetry limits. Furthermore, indications for the 1_ms⁺ excitation of ¹⁰⁸Cd were found. In total we established more than 120 new states and more than 580 new transitions, 30 spins and 80 multipole mixing ratios were determined and eight effective lifetimes stem from DSAM. This huge amount of new data enabled an investigation of the excitation spectrum even under statistical aspects. We discuss the frequency of spin values below 3.13 MeV in the framework of the constant temperature model.