The de-excitation gamma radiation following inelastic scattering of neutrons has been studied for eight elements (of normal isotopic abundance) with excited states between 100 and 350 kev. A thin Nal(Tl) crystal spectrometer is used as a gamma-ray detector. Yield curves for the gamma rays from low-lying levels in manganese, iodine, hafnium, tantalum, wolfram, rhenium, platinum, and gold have been obtained as a function of neutron energy for neutrons from 100 to 1800 kev. In some cases these yield curves represent a composite of gamma radiation from the directly excited states under observation, and cascade radiation from higher excited states. A comparison of the yield with total inelastic scattering cross sections requires a complete knowledge of the decay schemes. This is discussed for the individual elements. In the cases of Mn, I, and Re cross-section values obtained represent that part of the total inelastic cross section which arises from the excitation of a single known level.Agreement of the excitation curves with Hauser-Feshbach theory is good in most cases. No large unanticipated effects seems to arise in the inelastic scattering of neutrons from levels known to be rotational. * Supported in part by the joint program of the Office of Naval Research and the U. S. Atomic Energy Commission. f Also at Wellesley College. iR. M. Kiehn and C. Goodman, Phys. Rev. 95, 987 (1954); R. B. Day, Phys. Rev. 89, 908(A) (1953). 2 A.
Using liquid argon in a specially designed Dewar flask, Li 7 (/>,w) neutrons, and a hydrogen recoil counter, we have measured er*(A) at 2-kev intervals in the range 450 to 1100 kev of neutron energy. The experiment was performed in good geometry using the transmission method.
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