Neutron spectra were measured by the time of flight method using a rotating disk chopper system in the JRR-3M prompt gamma
ray analysis system. Effective g-factors for non-1/v elements such as Cd, Sm and Gd were calculated from the measured neutron spectra and the neutron cross section data, and
they was used for correcting the k0-factors. The resulting k0-factors for the cold and thermal neutron beams agreed within 10%. Furthermore, the prompt gamma ray emission probabilities
of Cd, Sm and Gd were derived from the corrected k0-factors using other relevant physical constants.