Spectroscopic study of Ni via cold neutron capture reaction, 1; Nuclear structure of Ni

Oshima, Masumi; Kin, Tadahiro*; Nakamura, Shoji  ; Homma, Michio*; Minato, Futoshi   ; Hayakawa, Takehito; Hara, Kaoru; Kimura, Atsushi   ; Koizumi, Mitsuo ; Harada, Hideo   ; Goto, Jun*; Murakami, Yukihiro*

The -radiation has been investigated produced by cold neutron capture in an enriched Ni sample. The 315 -rays have been placed in the Ni level scheme of which 272 placements are new. We have determined excitation energies with 0.2-0.8 keV error and branching ratios of 62 bound levels in Ni, including 30 new levels. The Q-value of the Ni (n,) Ni reaction amounts to 6837.75 (18) keV. A large-scale shell-model calculation has been performed and the energies of the low-lying Ni states are successfully reproduced. A mean-field statistical model calculation has been also made by using a self-consistent interaction between the Hartree-Fock + BCS method and the statistical calculation. The calculation result is consistent with the experimental level density of Ni.