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Slow Neutron Velocity Spectrometer Studies. II. Au, In, Ta, W, Pt, Zr

1947; American Institute of Physics; Volume: 71; Issue: 3 Linguagem: Inglês

10.1103/physrev.71.165

1536-6065

W. W. Havens, C. S. Wu, L.J. Rainwater, C. L. Meaker,

Nuclear reactor physics and engineering

The slow neutron velocity spectrum of Au, In, Ta, W, Pt, and Zr have been investigated. The results for Au and In check the values previously obtained using the "old" system. The results for the gold level at (4.8\ifmmode\pm\else\textpm\fi{}0.1)ev with ${\ensuremath{\sigma}}_{0}{\ensuremath{\Gamma}}^{2}=600$, and for the main indium level at (1.44\ifmmode\pm\else\textpm\fi{}0.02) ev with ${\ensuremath{\sigma}}_{0}{\ensuremath{\Gamma}}^{2}=210$ agree with the earlier results. Additional indium levels were found at (3.8\ifmmode\pm\else\textpm\fi{}0.2) ev with ${\ensuremath{\sigma}}_{0}\ensuremath{\Gamma}\ensuremath{\sim}120$ and at (8.6\ifmmode\pm\else\textpm\fi{}0.4) ev with ${\ensuremath{\sigma}}_{0}\ensuremath{\Gamma}\ensuremath{\sim}300$. The cross-section curve for Ta below 1 ev is well matched by $\ensuremath{\sigma}=[(7.2\ifmmode\pm\else\textpm\fi{}0.4)+(3.0\ifmmode\pm\else\textpm\fi{}0.1){E}^{\ensuremath{-}\frac{1}{2}}$. Tantalum has levels at (4.1\ifmmode\pm\else\textpm\fi{}0.1) ev with ${\ensuremath{\sigma}}_{0}{\ensuremath{\Gamma}}^{2}\ensuremath{\sim}44$, at (10.0\ifmmode\pm\else\textpm\fi{}0.3) ev with ${\ensuremath{\sigma}}_{0}{\ensuremath{\Gamma}}^{2}\ensuremath{\sim}25$, at (13\ifmmode\pm\else\textpm\fi{}0.5) ev with ${\ensuremath{\sigma}}_{0}{\ensuremath{\Gamma}}^{2}\ensuremath{\sim}3$, at (22\ifmmode\pm\else\textpm\fi{}2) ev with ${\ensuremath{\sigma}}_{0}{\ensuremath{\Gamma}}^{2}\ensuremath{\sim}18$, at (37\ifmmode\pm\else\textpm\fi{}3) ev with ${\ensuremath{\sigma}}_{0}{\ensuremath{\Gamma}}^{2}\ensuremath{\sim}400$, and other dips probably indicating multiple strong levels near 100 ev, 300 ev, and at higher energies. The cross section curve for W below 1 ev is well matched by $\ensuremath{\sigma}=[(5.7\ifmmode\pm\else\textpm\fi{}0.2)+(2.72\ifmmode\pm\else\textpm\fi{}0.05){E}^{\ensuremath{-}\frac{1}{2}}]$. There are levels at (4.0\ifmmode\pm\else\textpm\fi{}0.1) ev with ${\ensuremath{\sigma}}_{0}{\ensuremath{\Gamma}}^{2}\ensuremath{\sim}13$, at (7.4\ifmmode\pm\else\textpm\fi{}0.2) ev with ${\ensuremath{\sigma}}_{0}{\ensuremath{\Gamma}}^{2}\ensuremath{\sim}5$, at (18.0\ifmmode\pm\else\textpm\fi{}0.5) ev with ${\ensuremath{\sigma}}_{0}{\ensuremath{\Gamma}}^{2}\ensuremath{\sim}3000$ (perhaps multiple), at (45\ifmmode\pm\else\textpm\fi{}2) ev with ${\ensuremath{\sigma}}_{0}{\ensuremath{\Gamma}}^{2}\ensuremath{\sim}400$ (perhaps multiple), at (180\ifmmode\pm\else\textpm\fi{}20) ev with ${\ensuremath{\sigma}}_{0}{\ensuremath{\Gamma}}^{2}\ensuremath{\sim}10,000$ if single (probably multiple), and a dip at 1100 ev which is probably multiple. The results for Pt show pronounced crystal interference effects in the thermal region. The $\frac{1}{v}$ line is probably $\ensuremath{\sigma}=[(12.0\ifmmode\pm\else\textpm\fi{}0.3)+(1.03\ifmmode\pm\else\textpm\fi{}0.06){E}^{\ensuremath{-}\frac{1}{2}}]$. There are levels at (11.5\ifmmode\pm\else\textpm\fi{}0.4) ev with ${\ensuremath{\sigma}}_{0}{\ensuremath{\Gamma}}^{2}\ensuremath{\sim}55$, at (18.2\ifmmode\pm\else\textpm\fi{}1) ev with ${\ensuremath{\sigma}}_{0}{\ensuremath{\Gamma}}^{2}\ensuremath{\sim}30$, and broad dips near 100 ev and near 1000 ev indicating the presence of several strong unresolved levels. The results for Zr below 0.6 ev are well matched by $\ensuremath{\sigma}=[(6.8\ifmmode\pm\else\textpm\fi{}0.3)+(0.74\ifmmode\pm\else\textpm\fi{}0.10){E}^{\ensuremath{-}\frac{1}{2}}]$. There are weak levels at (1.09\ifmmode\pm\else\textpm\fi{}0.03) ev with ${\ensuremath{\sigma}}_{0}\ensuremath{\Gamma}\ensuremath{\sim}5$ and at (2.30\ifmmode\pm\else\textpm\fi{}0.07) ev with ${\ensuremath{\sigma}}_{0}\ensuremath{\Gamma}\ensuremath{\sim}8$. A complex dip near 7 ev probably consists of two levels at ${E}_{0}=(5.7\ifmmode\pm\else\textpm\fi{}0.5)$ ev with ${\ensuremath{\sigma}}_{0}\ensuremath{\Gamma}\ensuremath{\sim}10$ and at (7.6\ifmmode\pm\else\textpm\fi{}0.4) ev with ${\ensuremath{\sigma}}_{0}{\ensuremath{\Gamma}}^{2}\ensuremath{\sim}40$.