Study on the 90Zr(7Li, 7Be)90Y reaction at E7Li=78 MeV

The reaction 90Zr(7Li, 7Be)90Y is studied at 7Li energy of 78 MeV in the 10-28 deg angular range. At all angles the energy spectra show a structure which is associated with particle-hole excitations of the 90Y nucleus and his maxima at Ex=1.7 and 4.6 MeV. The experimental results are analyzed by the DW method using the transition densities for states found in the theory of finite Fermi systems. The hard part of the 7Be energy spectrum is shown to be due to the charge-exchange one-step mechanism. When Ex grows, the multi-step processes become more important. According to the calculations, at excitaion energies Ex=0-3 MeV the dominant contribution comes from transitions with Lt=1 and 3, and at Ex>8 MeV transitions with Kt=4 and 6 dominate. In the range Ex=3-7 MeV the cross sections are almost equally defined by the above presented multipolarities