Above-Barrier Enhancement of Fusion in the ~6He + ~(209)Bi Nuclear Reaction

摘要

The fission cross sections for the ~6He + ~(209)Bi reaction as functions of the ~6He-beam energy are measured. The experimental excitation functions for the reaction ~(209)Bi(~6He, 4n)~(211) At are also presented. The ~6He secondary ion beam is obtained on the basis of the extracted-beam transport system of the U400-M accelerator (the Q4DQ spectrometer).A comparison of the experimental data obtained with available results for the ~6He + ~(209Bi reaction shows that a pronounced enhancement of the fission cross sections in the above-barrier energy region is observed in the case of the reaction with the ~6He beam. In order to fit the results of theoretical calculations to the experimental data, it is necessary to reduce the Coulomb barrier by 15% (20%). This corresponds to an increase of 1.5 (1.6) fm in the parameter r_0 of the nuclear potential.