Measurement of the ionization probability of the 1s σ MO on the way into the nuclear fusion reaction58Ni+54Fe

The total excitation probability of the 1s σ molecular orbital on the way into the nuclear reaction58Ni+54Fe at 238 MeV has been directly measured. The result found is (3.1±0.6) 10−2. The method is based on the detection at zero degree with respect to the beam direction of the x-rays emitted in the reaction, in coincidence with the gamme rays following the deexcitation of the evaporation residues produced in the nuclear reaction. The difference in the doppler shift of the x-ray energies enables to discriminate between the internal conversion x-rays and the prompt atomic x-rays following the decay of the vacancies made in the approach of the nuclear reaction. The experimental data is compared with numerical evaluations of different mechanisms which can produce a vacancy in theK-shell of the united atom at the end of the collision. The best agreement is found with the value of the direct ionization of the 1sσ MO evaluated in the framework of the Brigg's model.