Neutron Total Cross Sections of Even Isotopes of Zr in the Energy Range 2-60 keV

The zirconium nuclei are located at the beginning of the region of masses, viz., about 90-130, in which the measured strength functions are anomalously small, as far as the original optical model is concerned. We have examined the neutron resonance structure of${}_{}{}^{90,92,94,96}{}_{}{}^{}\mathrm{Zr}$ in the energy region $2\mathrm{keV}<E_n<60\mathrm{}\mathrm{keV}$, and we find that the $s$-wave strength function, in the region in which the $s$ waves can be identified, has a mean value of (1.2±0.4)×${10}^{-4\mathrm{}}$. At energies roughly above 25 keV, the ratio of the mean resonance width at 1 eV to the mean resonance spacing rises to a value of (2.5±0.6)×${10}^{-4\mathrm{}}$; the latter value can not be uniquely interpreted because $s$-wave identification is not positive. Level densities for nuclides with neutron numbers in the vicinity of the magic number 50 are considered.