Properties ofs-Wave andp-Wave Neutron Resonances in Niobium

Abstract

The neutron resonances of niobium were studied with the Argonne fast chopper. The transmission of a series of four samples was measured over the range of energy from 10 to 10 000 ev. Resonance parameters were deduced for thirteen levels, those below 700 ev. An examination of these parameters, calculations with the optical model, and a comparison of the cross sections at low and high energy all indicate that some of the resonances, even those below 100 ev, are due to a $p$-wave process. By using this evidence, average parameters are deduced. The radiation width is found to be 0.22 ev. The strength function $\frac{{{\overline{\ensuremath{\Gamma}}}_{n}}^{0}}{\overline{D}}$ for $s$-wave neutrons is 0.10\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$. The value of the corresponding quantity for $p$-wave neutrons is 4.6\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$. The resonance absorption integral deduced from the parameters is found to be in agreement with the result of a "pile oscillator" measurement.