Gamma-Ray Spectrum from Thermal-Neutron Capture inHf177and Associated Energy Levels inHf178

Abstract

The gamma-ray spectrum resulting from thermal-neutron capture in ${\mathrm{Hf}}^{177}$ was investigated with the Argonne 7.7-m bent-crystal spectrometer. The observed spectrum consisted of 217 gamma rays with energies between 50 keV and 1.6 MeV. These precision measurements of gamma-ray energies and intensities were used to modify and extend the level scheme of ${\mathrm{Hf}}^{178}$. The proposed level scheme of ${\mathrm{Hf}}^{178}$ contains the following 20 levels (the energy of the level being given in keV followed by the $K$ value, spin, and parity of the level): ground state [0,$0^{+}$]; 93.17 [0,$2^{+}$]; 306.59 [0,$4^{+}$]; 632.10 [0,$6^{+}$]; 1058.3[[0,$8^{+}$]]; 1196.27 [0,$0^{+}$]; 1237.26 [[0,$0^{+}$]]; 1269.34 [0,$2^{+}$]; 1322.85 [0,$2^{+}$]; 1384.48 [[,4]]; 1402.25 [2,$2^{+}$]; 1420.64 [2,$2^{+}$]; 1431.25 [0,$0^{+}$]; 1473.13 [(1,$1^{+}$) or (2,$2^{+}$)]; 1473.32 [0,$4^{+}$]; 1512.92 [0,$4^{+}$]; 1514.56 [[,$2^{+}$]]; 1550.02 [[2,$3^{+}$]]; 1569.78 [[2,$3^{+}$]]; and 1575.73 [[0,$2^{+}$]]. The double brackets indicate an uncertainty in the assignments.