Lifetime Measurement of the 2⁺ Excited State in ⁷⁸Y: Isospin Breaking Effects in N=Z Nuclei

An unexplained staggering of B(E2: 2⁺ → 0⁺) values has been seen between odd-odd and even-even nuclei along the N=Z line. This effect is most pronounced in ⁷⁸Y, which has only been studied a few times. The first study used recoil beta tagging (RBT) for channel selection in a fusion-evaporation reaction at JYFL in Finland with JUROGAM2 which identified the (2⁺) state. The level scheme was later extended up to the (10⁺) state in another fusion-evaporation reaction at JYFL. The second experiment was carried out at NSCL, pre-FRIB, using a knock-out reaction. In this study the lifetime of the 2⁺ state was measured via line shape analysis, resulting in an unexpectedly low B(E2) value. To confirm the result, a fusion-evaporation reaction ⁴⁰Ca (⁴⁰Ca, pn) ⁷⁸Y was carried out at the Argonne Tandem Linac Accelerator system (ATLAS) with the integrated Cologne Argonne plunger setup (iCAPS) and Gammasphere. Channel selection was done using Neutron Shell and Microball. The main goal of the analysis is to measure the lifetime of the (2⁺) state using the differential decay-curve method (DDCM) and possibly a gate on an in-flight decay of a feeding transition. The second goal of the analysis is to further explore the level scheme using the capabilities of Gammasphere, as only a few levels at low-lying energies have been identified. This will give further insight into isospin breaking effects.