Neutron resonance spectroscopy:Hf177

Abstract

High resolution neutron time of flight spectroscopy measurements were made for a sample enriched in $^{177}\mathrm{Hf}$ using the Columbia University Nevis synchrocyclotron. The measurements used the 202.05 m flight path for transmission measurements and the 39.37 m flight path for capture measurements. We obtained (${E}_{0}$, $g{\ensuremath{\Gamma}}_{n}^{0}$) resonance parameters for 176 levels in $^{177}\mathrm{Hf}$ to 700 eV and 12 levels in $^{178}\mathrm{Hf}$ to 720 eV. We also obtained ${\ensuremath{\Gamma}}_{\ensuremath{\gamma}}$ values for 25 levels in $^{177}\mathrm{Hf}$, givirg $〈{\ensuremath{\Gamma}}_{\ensuremath{\gamma}}〉=65$ meV. The $s$ wave strength function for $^{177}\mathrm{Hf}$ is found to be (2.70 \ifmmode\pm\else\textpm\fi{} 0.25). Most $s$ levels were detected to 100 eV, but many were missed above 100 eV. An analysis favors $〈{D}_{0}〉=(2.22\ifmmode\pm\else\textpm\fi{}0.13)$ eV for the "true" $s$ level spacing in $^{177}\mathrm{Hf}$. The results to 100 eV are in reasonable agreement with predictions for statistical orthogonal population ensembles.NUCLEAR REACTIONS $^{177}\mathrm{Hf}(n, n)$, ($n, \ensuremath{\gamma}$), $E=3\ensuremath{-}700$ eV; measured ${\ensuremath{\sigma}}_{t}(E)$; deduced ${E}_{0}$, $g{\ensuremath{\Gamma}}_{n}^{0}$, ${\ensuremath{\Gamma}}_{\ensuremath{\gamma}}$, ${S}_{0}$, $〈{D}_{0}〉$, $\frac{{S}_{0}(J=4)}{{S}_{0}(J=3)}$; orthogonal ensemble tests.