| Popis: |
High-resolution transmission and capture measurements of $^{60}\mathrm{Ni}$-enriched targets have been made from a few eV to 1800 keV in transmission and from 2.5 keV to 5 MeV in capture. The transmission data from 1 to 452 keV were analyzed with a multilevel $R$-matrix code which uses Bayes' theorem for the fitting process. This code provides the energies and neutron widths of the resonances inside the 1- to 452-keV region as well as a possible parametrization for outside resonances to describe the smooth cross section in this region. The capture data were analyzed from 2.5 to 452 keV with a least-squares fitting code using the Breit-Wigner formula. Average parameters for the 30 observed $s$-wave resonances were deduced. The average level spacing, ${D}_{0}$, was found to be equal to 15.2\ifmmode\pm\else\textpm\fi{}1.5 keV; the strength function, ${S}_{0}$, equal to (2.2\ifmmode\pm\else\textpm\fi{}0.6)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$; and the average radiation width, ${\overline{\ensuremath{\Gamma}}}_{\ensuremath{\gamma}}$, equal to 1.30\ifmmode\pm\else\textpm\fi{}0.07 eV. The staircase plot of the reduced level widths and the plot of the Lorentz-weighted strength function averaged over various energy intervals show possible evidence for doorway states. The level densities calculated with the Fermi-gas model for $l=0$ and for $lg0$ resonances were compared with the cumulative number of observed resonances, but the analysis is not conclusive. The correlation coefficient $\ensuremath{\rho}$ between ${\ensuremath{\Gamma}}_{n}^{0}$ and ${\ensuremath{\Gamma}}_{\ensuremath{\gamma}}$ is equal to 0.53\ifmmode\pm\else\textpm\fi{}0.18. The average capture cross section as a function of the neutron incident energy is compared to the tail of the giant electric dipole resonance prediction.NUCLEAR REACTIONS $^{60}\mathrm{Ni}(n, n)$, ${E}_{n}=1\ensuremath{-}452$ keV; $^{60}\mathrm{Ni}(n, \ensuremath{\gamma})$, ${E}_{n}=2.5\ensuremath{-}452$ keV; measured ${\ensuremath{\sigma}}_{n,\mathrm{tot}}({E}_{n})$, ${\ensuremath{\sigma}}_{n,\ensuremath{\gamma}}({E}_{n})$; deduced $^{61}\mathrm{Ni}$ resonance parameters ${E}_{0}$, $g{\ensuremath{\Gamma}}_{n}$, ${\ensuremath{\Gamma}}_{\ensuremath{\gamma}}$, $l$, $J$, and average properties ${D}_{0}$, ${S}_{0}$, ${\overline{\ensuremath{\Gamma}}}_{\ensuremath{\gamma}}$; calculated level density for $l=0$ and $lg0$ resonances and correlation $\ensuremath{\rho}({\ensuremath{\Gamma}}_{n}^{0}, {\ensuremath{\Gamma}}_{\ensuremath{\gamma}})$. |
