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 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.

Fast-Neutron Scattering From Tantalum, Rhenium, and Platinum.

“…The elements tantalum, rhenium, and platinum consist of such nuclei. They are similar in mass and charge, but vary in deformation, 6, from -0.3 (Ta) to -0.15 (Pt).1' Previous experimental studies of neutron scattering from these elements have been largely confined to a few incident neutron energies and/or have provided little knowl- [3][4][5][6][7][8][9][10][11][12] edge of the inelastically scattered neutron spectrum. Because of this limited experimental base, quantitative comparison with calculation has been difficult.…”

Detection of Fast Neutrons with Nal(Tl) Crystal

“…(1) Nai activation by slow neutrons (2) Radiative capture of low energy neu· trons, mostly in 127 1 (3) Inelastic scattering of fast neutrons, mostly by 127 1 This suggested to the present author the possibility of measuring neutron flux through the detection of the 'Y-rays from these inter· actions.…”

“…The inelastic reaction of 127 l(n, n''Y) was studied with the use of thin Nal scintillator< 3 l, and analysis was conducted on 'Y -rays of energies down to 30 keV, which corresponds to the excitation energies in 127 1 nuclei. Good agreement was obtained with values given by Davis, et at.…”