Is the 4.742 MeV state in ~(88)Sr the 1~- two-phonon state?

摘要

A nuclear resonance fluorescence experiment on ~(88)Sr has been performed with bremsstrahlung of 6.7 MeV endpoint energy. The γ-ray linear polarisation has been measured with a EUROBALL CLUSTER detector used as a Compton polarimeter. The results indicate positive parity for the J = 1 state at 4.742 MeV in ~(88)Sr, in contrast to the previous interpretation as a 1~- two-phonon (2_1~+ direct X 3_1~-) state and in conflict with the predictions of the quasiparticle-phonon model. On the basis of such calculations the 1~+ state at 3.486 MeV may be considered as the 1_1~+ one-phonon state and the very strong 1_1~+ → 0_1~+ deexcitation as proton spin-flip 2p_(1/2) → 2p_(3/2) transition.