Neutron Resonance Spectroscopy. XII. The Separated Isotopes of W

The results of neutron resonance time-of-flight spectroscopy measurements using the Nevis synchrocyclotron are given for the separated W isotopes (182, 184, 186) and for natural W. Almost all s levels were observed to 2.65 keV, and resonance (g)Γₙᵒ values presented to {~}16 keV for the above even isotopes, and to 700 eV and 2.6 keV, respectively, for ¹⁸³W. The ¹⁸³W level assignments were from levels in natural W which were not assigned to the other isotopes. A Bayes's theorem analysis shows that nearly all of the observed levels are s rather than p levels, since W is at a maximum for the s strength function S₀ but not for S₁, and the level detection sensitivity was not sufficient to detect other than exceptionally strong p levels. We were able to assign J values to 14 s levels of ¹⁸³W. The 41 observed ¹⁸²W levels to 2.65 keV and the 52 ¹⁸³W levels to 701 eV seem to be pure complete s populations, being fitted excellently by the Wigner nearest neighbor spacing theory and the Porter-Thomas reduced neutron width distribution. The orthogonal ensemble (OE) theory was found to be in good agreement with the ¹⁸²W and ¹⁸³W data. The ¹⁸⁴W level set to {~}2.6 keV also seems to be an essentially complete, pure, s population sample. While it agreed within statistical limits to the above statistical theories, it gave poorer discrimination against alternate theories. Tests suggested that a few s levels in ¹⁸⁶W had been missed to {~}2.6 keV. The 10⁴Sₒ values are 2.40 ±{} 0.31, 1.65 ±{} 0.32, 2.35 ±{} 0.24, and 2.23 ±{} 0.27 for 182, 183, 184, and 186, respectively. The $〈D〉$ values for s populations are 66.3 ±{} 3.2 eV (182), 13.2 ±{} 0.7 eV (183), 81.3 ±{} 5.1 eV (184), and 90 ±{} 7 eV (186). A useful and accurate method for evaluating the Doppler-broadening integrals is described.