The total cross sections for the reactions 7 Li(£,£') 7 Li(478 keV) and 7 Li(£,ra) 7 Be(431 keV) have been measured for proton energies between 23 and 52 MeV and compared with the predictions of a microscopic model of the reaction. The spin-flip, isospin-flip part of the effective interaction is found to be essentially independent of energy, whereas the pure central part appears to decrease with increasing energy.

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The total cross section for the 6 Li(^,^') 6 Li(3.56 MeV) reaction was measured by observing the isotropic 3.56-MeV de-excitation y rays in a 20-cm 3 Ge(Li) detector and was found to decrease slowly with energy. In a microscopic model of the reaction, this cross section depends only on the spin-isospin-dependent part Fn of the effective interaction. At energies above 34 MeV, the data are well described by a potential, Vn= Ve-ar /ar, where the range 1/a is taken to be 1.0 F, and F= 12.1 MeV. At 25 MeV, F= 11.1 MeV fits the data. The impulse approximation predicts a cross section larger than the data for the energy range of this experiment, the ratio decreasing from 2.9 at 25 MeV to 1.4 at 45 MeV. Available evidence on the spinisospin-dependent interaction is summarized. For proton energies between 23 and 52 MeV, the strength of Vu lies in the range 12.5±2.5 MeV and does not appear to vary with energy.

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