Lifetime of the first excited 2~+ state in ~(172)W and ~(178)W

摘要

The lifetime of the first excited 2~+ state in ~(172)W and ~(178)W has been measured in fast timing experiments using the Cologne Double Orange Spectrometer for conversion electron spectroscopy. The B(E2,2_1~+→0_1~+) values of the isotopes ~(170-178)W are compared to calculations in the Interacting Boson Model (IBM) employing the consistent Q formalism. An analysis of the B(E2) value systematics in the rare earth nuclei around mass A=170 using the N_pN_n-scheme shows signatures of a structural change in the tungsten isotopes which is not reflected in the energy systematics.