Excitation of Some Low-Lying Levels by Inelastic Neutron Scattering

Abstract

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 NaI(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.