The Energy Dependence of the Resonant Scattering of Slow Neutrons from Gold

Abstract

The energy dependence of slow neutrons scattered from a thick gold target has been measured using a newly developed scattering chamber in conjunction with the Columbia slow neutron velocity spectrometer. A method of analysis has been developed for determining the ratio of the scattering cross section to the total cross section, a 8 /<rt, as a function of energy for an "unknown" sample in terms of a calibration target for which (<T a /a t )(E) is known.The agreement between the experimental determination of {a s /<r t )(E) for gold in the energy range 0.7 to 8 ev and the Breit-Wigner theory is excellent. All the level parameters can be evaluated by combining these scattering data with the results of transmission experiments and the cross section for self-indication. The final results for the 4.9-ev gold level are: /= 1, T = 0.172 ev, r A =0.0211 ev, Rj^= 1.03 barn*, Rj^i = Q.9\7 barn*.

Shell Effects in Highly Excited Nuclei

“…Even as far away from the magic number as 79A11 197 the spacing is definitely anomalous (about 60 ev). 3 - 15 The even elements show a similar behavior just below 126 neutrons. 8 2Pb 208 appears to have only one s resonance between 0 and 800 kev 16 ; 82Pb 206 has many s resonances with a spacing of the order of 20 kev, 16 while an examination of the cross-section curves of even elements 3 between 8 oHg and 74W reveals a qualitative increase of spacing for the heavier elements.…”

Neutron Scattering and Capture Cross-Section Measurements

“…Perhaps the earliest measurements of resonance elastic scattering made use of the Columbia Velocity Selector (Rainwater et al, 1947) and were made on the 4.9 eV resonance in gold (Tittman et al, 1950;Tittman and Sheer, 1951) and 5.2 and 16 eV resonances in silver (Sheer and Moore, 1955). Thick samples were used with BF 3 detectors, and only first-order scattering corrections were made.…”