A new isomeric state in 218Pa

The decay of 218Pa was investigated by means of α and γ spectroscopy. The nucleus was produced in the fusion reaction 40Ar+182W and separated in flight by the gas-filled recoil separator SHANS (Spectrometer for Heavy Atoms and Nuclear Structure). The known α decays of 218Pa were measured with improved precision and newly assigned to be originating from the ground state, which clarified the ambiguities in their previous assignments. In addition, a new isomeric state in 218Pa decaying with α-particle energies of 9691(15) keV, 9595(21) keV and a half-life of 135−32+62 μs was identified. The spins and parities of the involved states were tentatively assigned on the basis of the systematic α-decay properties of the odd-proton N=127 isotones and shell model calculations. Keywords: Odd-proton N=127 isotones, Isomeric state, α-particle energy, Half-life, Shell model calculation, Spin and parity