Spectra of γ-rays from capture of 2 eV to 9 x 10⁴ eV neutrons by ¹⁸¹Ta

Using new experimental techniques, the spectra of γ-rays from the capture of neutrons by ¹⁸¹Ta were measured at the Livermore 100-MeV linac for neutrons from 2 eV to 9 x 10⁴ eV with a (Ge(Li)-NaI) three-crystal spectrometer. Individual primary γ-ray lines were resolved to 1778-keV excitation in ¹⁸²Ta. Neutron resonances were resolved to 200-eV neutron energy. Data analysis techniques and codes were developed to extract positions and intensities of resolved transitions from the large data matrices accumulated in this experiment. Techniques were developed to unfold the unresolved γ-ray spectra using the simple response of the three-crystal spectrometer. The resolved transition data were used to place 110 states with spin and parity assignments in the ¹⁸²Ta level diagram below 1780-keV excitation. A set of 1240 E1 transition strengths were analyzed to extract 1.38 +- 0.11 degrees of freedom for the most likely chisquared fit to the distribution of widths. The E1 strength function was extracted for E/sub gamma/ = 4 to 6 MeV and compared with previous results. The γ-ray spectra for E/sub gamma/ = 1.5 to 6.1 MeV were unfolded for neutron energy groups between 20 and 9 x 10⁴ eV. Below 5-MeV γ-ray energy no dependence of the spectral shape on neutron energy was observed. (author)