Spectrum ofγrays in the 8- to 20-MeV range fromCf252spontaneous fission

Abstract

The spectrum of $\gamma$ rays in the 8- to 20-MeV range has been measured for ${}_{}{}^{252}{}_{}{}^{}\mathrm{Cf}$ spontaneous fission using a 25.4 cm×25.4 cm NaI crystal and time-of-flight separation of $\gamma$ rays and neutrons. These data, obtained at three solid angles, are in disagreement with the recent result of Brooks and Reines that $\gamma$-ray events above 10 MeV in their experiment were due to two correlated $\gamma$ rays detected simultaneously. A statistical calculation using the Hauser-Feshbach formalism was performed for the deexcitation of the highly excited fission fragments. The computed $\gamma$-ray spectrum in the energy range 8-17 MeV has the same shape as the measured spectrum but is lower than the measurement by a factor of 3 to 4.