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Description
Quadrupole interaction between protons and neutrons drives the nucleus into deformed configurations at low excitation energies. The $^{83}$Se nucleus is at the mid of the proton fp-shell (Z=28-40), it is a good candidate to study the properties of particle-hole intruder states lowered in energy by large quadrupole correlations. Lifetime measurement of the low-lying intruder state with spin 1/2$^{+}$, originating from s$_{1/2}$, will provide information on its wave function and allow one to estimate the degree of N = 50 core breaking in the ground state of Se isotopes.
The lifetime of the 500-keV 1/2$^+$ level was measured using the Recoil Distance Method. A beam of 82Se, with intensity 0.02 pnA accelerated at 270 MeV from TANDEM accelerator at LNL-INFN, impinged into a deuterated polyethylene (C2D4) target which was evaporated on a 6 mg/cm2 thick gold layer. The GALILEO γ-array was coupled to the SPIDER silicon array, allowing one to obtain the needed channel selectivity through coincidence measurements between γ rays and protons coming from the (d,p) reaction.
