STUDY OF THE REACTION (GAMMA,PF) ON U-235, U-238, AND NP-237 NUCLEI WITH TAGGED PHOTONS IN THE ENERGY-RANGE 60-240-MEV

The relative probabilities of the emission of preequilibrium charged p articles with Z = 1 (protons and deuterons) were measured in coinciden ce with the fragments of U-235, U-238 and Np-237 fission induced by qu asimonochromatic tagged photons of energy in the range 60 - 240 MeV. T he experiment was carried out at the ROKK-2 facility of the storage ri ng VEPP-3 (Institute of Nuclear Physics, Novosibirsk) using a nuclear- fragment detector. The fission fragments were detected by low-pressure multiwire proportional chambers. Light particles were detected by the telescope of the plastic scintillation counters. The probability of p roton emission per decay event was shown to be similar to 20%. It depe nds only slightly on photon energy in the range under investigation. T his result is in agreement with the predictions of the cascade-evapora tion model.