Photofission of Al-27 nucleus in the quasi-deuteron region of photonuclearabsorption

Quasi-monochromatic photon beams of 108 MeV Compton-edge energy produced in the ROKK-1M facility at the storage ring VEPP-4M (BINP, Novosibirsk) and m akrofol sheets as fission track detectors were used to measure the photofis sion yield of Al-27. The fission yield was found to be (160 +/- 55) mu b. F rom this result and previously measured Al-27 photofission yield at similar to 79 MeV end-point energy with the LADON apparatus, the trends of fission cross section and fissility have been obtained in the incident photon ener gy range similar to 40-110 MeV. The present results and data for other inte rmediate-mass nuclei obtained with the same methodology indicate an increas e of fissility with decreasing Z(2)/A as predicted by the liquid drop model for fissioning systems lighter than similar to Ag.