Deformation effect in the fast neutron total cross section of aligned /sup 59/Co

The variation of the total neutron cross section, $\ensuremath{\Delta}{\ensuremath{\sigma}}_{\mathrm{align}}$, on $^{59}\mathrm{Co}$ due to nuclear alignment of the target has been measured over the energy range from 0.8 to 20 MeV employing a cobalt single crystal with a 34% nuclear alignment. The results show that $\ensuremath{\Delta}{\ensuremath{\sigma}}_{\mathrm{align}}$ oscillates from a minimum of -5% at about 2.5 MeV to a maximum of + 1% at about 10 MeV. The data were successfully fitted by optical model coupled-channel calculations. The coupling terms were deduced from a model representing the $^{59}\mathrm{Co}$ nucleus as a vibrational $^{60}\mathrm{Ni}$ core coupled to a proton hole in a ($1{f}_{\frac{7}{2}}$) shell, without free parameters. The optical model parameters were determined by fitting the total cross section, which was independently measured. The theoretical calculations show that, at lower energies, $\ensuremath{\Delta}{\ensuremath{\sigma}}_{\mathrm{align}}$ depends appreciably on the coupling with the low-lying levels.