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the photofission of '"U with 12-, 1S-, 20-, 30-, and 70-MeV bremsstrahlung. Changes in the characteristics of the mass distribution are studied. An enhanced yield in the mass region 133-134, decreasing with increasing end-point energy of the bremsstrahlung {E, ), is observed. From the determined independent yields the most probable charges Z (F. ,) are calculated using the value 0.8S for the width parameter c of the charge distribution as deduced from our results for mass chain 134. The determined Z (F. ,) values are very we11 described by the empirical relation of Nethaway except for the mass chain 136. This discrepancy for mass chain 136, which decreases with increasing end-point energy of the bremsstrahlung, is attributed to an abnormal low yield of " Cs. Fragment shell effects are discussed. From the isomeric ratios for ' 'Teg-' 'Te and ' P-' I average initial fragment spins are calculated using a statistical model analysis. NUCLEAR REACTIONS, FISSIONU(y', E), Ey m~=12, 15, 20, 30, 70 MeV; measured: fragment p-ray spectra; deduced: mass distributions, most probable J charges, isomeric ratios, average initial fragment spins.

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