Electron Spin in Semiconductors

The excitation function of the y-rays following inelastic scattering was obtained from the difference curves taken at a number of neutron bombarding energies, the neutrons a t the scatterer having an energy spread of 70 kev.T h e relative y-ray intensity at each energy was determined by adding together all counts between 7 and 14 volts pulse height, a correction being made, where necessary, for a small contribution from the lower energy group.The results are given in fig. 2 .I t will be observed that the threshold for the reaction i s close to the value of 0.S1 MeV expected for the neutron energy spread used.An approximate estimate of 0.4 barn for the absolute cross section for inelastic scattering at a neutron energy of 1.23 MeV was obtained by calculating the crystal efficiency and assuming spherical symmetry of the y-radiation.This value is believed to be correct to a factor of two.We thank the Director,