Gamma Rays from Neutron Inelastic Scattering inB10,F19, andFe56

Abstract

The cross section for excitation of the 0.72-Mev gamma ray in the ${\mathrm{B}}^{10}(n, n^{\prime }\gamma ){\mathrm{B}}^{10}$ reaction has been measured for neutron bombarding energies from threshold to 5.2 Mev. Resonances were observed at 1.93 Mev, 3.31 Mev, 4.1 Mev, and 4.73 Mev, with evidence of a broad resonance at 2.6 Mev. The angular distributions of the 0.110-Mev and 0.197-Mev gamma rays in the ${\mathrm{F}}^{19}(n, n^{\prime }\gamma ){\mathrm{F}}^{19}$ reaction and the 0.847-Mev gamma ray in the ${\mathrm{Fe}}^{56}(n, n^{\prime }\gamma ){\mathrm{Fe}}^{56}$ reaction were also measured at a neutron energy of 2.56 Mev. The first of these was isotropic, as would be expected for the decay of a spin-½ level; the last two showed anisotropies but were symmetrical about 90°. The angular distribution of the ${\mathrm{Fe}}^{56}$ gamma ray agrees very well in both shape and absolute magnitude with calculations based on the statistical model. Since this model predicts angular distributions for ${\mathrm{Fe}}^{56}$ that have a strong dependence on the spin assumed for the excited state, it appears that such angular distribution measurements may be a useful technique in nuclear spectroscopy.