Lifetime measurement of the 2⁺₁, 4⁺₁ states in semi-magic ⁶⁰Ni

A ? -? coincidence Recoil Distance Doppler Shift measurement has been carried out on Ni-60 to re-measure the lifetime of the 2(1)(+) and 4(1)(+) states. The new lifetime of the 2(1)(+) state supports the adopted NNDC value but disagrees with the results of two more recent Doppler-Shift Attenuation Method measurements, which suggested a longer lifetime. The new result for the 4(1)(+) state's lifetime is significantly shorter than the one recommended in the latest NNDC compilation while also reducing its uncertainty. It therefore resolves an unclear situation, where an unexpected drop in transition strength appeared from 58Ni to Ni-60. Both values match very well with recently applied shell model calculations using the GXPF1A interaction.