THE KINETIC ENERGY OF Cs136 PRIMARY FRAGMENTS FROM FISSION OF U235

Abstract

The ranges of Cs¹³⁶, Cs¹³⁷, and Ba¹⁴⁰ fission fragments in aluminum have been measured using an anodizing technique to strip layers from the aluminum together with radiochemical methods to determine the fission products. The mean ranges are, in milligrams per square centimeter: Cs¹³⁶, 2.64; Cs¹³⁷, 2.91; and Ba¹⁴⁰, 2.82. The range distributions were of near-Gaussian form with the following percentage full widths at half height; Cs¹³⁶ 17.7; Cs¹³⁷, 17.0; and Ba¹⁴⁰, 17.5. The range–energy relationship of Bohr, R = const. A^1/2E^1/2Z^−2/3, was tested using the range data of Katcoff (7) and of Niday (2) together with the kinetic energy data of Milton and Fraser (15) and found to be accurate, within experimental error, over any limited range of fragment masses. Using this formula it then appears that the total kinetic energy in the fission mode leading to Cs¹³⁶ is ∼21 Mev less than normal.