Time duration of fission of 238U by 4He ions

We have observed and quantitatively studied the shadow (blocking) minima and angular distributions of fission fragments, which arise in bombardment of a single-crystal target of UO2 by a beam of 4He ions at energies 23, 25, 26, 28, 30, 33, and 35 MeV. A time delay of the fission events is observed in analysis of the measured depths and the difference of the depths of the shadow minima chi/sup 150degree/ and Δchi. The energy dependence of chi/sup 150degree/ and Δchi corresponds to the results of a model calculation with choice of parameters on the basis of other experimental data