Spectroscopic Study of63Ni via Cold Neutron Capture Reaction: I. Nuclear Structure of63Ni

Abstract

The γ-radiation has been investigated for 63 Ni produced by cold neutron capture in an enriched 62 Ni sample. The 315 γ-rays produced were placed in a 63 Ni level scheme, in which 272 placements are new. We determined the excitation energies with 0.2–0.8 keV error and the branching ratios of 62 bound levels in 63 Ni, including 30 new levels. The Q -value of the 62 Ni( n ,γ) 63 Ni reaction amounts to 6837.75±0.18 keV. A large-scale shell-model calculation was performed that included the four single-particle orbits of 0 f 7/2 , 1 p 3/2 , 0 f 5/2 , and 1 p 1/2 , assuming an inert 40 Ca core for negative-parity states, and those of 1 p 3/2 , 0 f 5/2 , 1 p 1/2 , and 0 g 9/2 , assuming a 56 Ni core for positive-parity states. The energies of the low-lying 63 Ni states were successfully reproduced. A mean-field statistical-model calculation was also performed by using a self-consistent interaction between the Hartree–Fock + Bardeen–Cooper–Schrieffer method and the statistical calculation. The calculation result is consistent with the experimental level density of 63 Ni.