A systematic study of the total β-decay half-lives and β-delayed neutron emission probabilities is performed. The β-strength function is treated within a self-consistent density-functional + continuum-quasiparticle-random-phase-approximation framework including the Gamow-Teller and first-forbidden transitions. The experimental total β-decay half-lives for the Ni isotopes with $A\le 76$ are described satisfactorily. The half-lives predicted from $A=70$ up to $A=86$ reveal fairly regular A behavior which results from simultaneous account for the Gamow-Teller and first-forbidden transitions. For $Z\approx 28$ nuclei, a suppression of the delayed neutron emission probability is found when the $N=50$ neutron closed shell is crossed and the neutron excess becomes more than one major shell. The effect originates from the high-energy first-forbidden transitions to the states outside the $Q_{\beta }\text{−}{B}_n$ window in the daughter nuclei.

• Received 9 September 2004

DOI:https://doi.org/10.1103/PhysRevC.71.065801