The Binding Energy ofLi6

The mass defect of ${\mathrm{Li}}^6$ has been calculated with the use of a symmetric Hamiltonian. Perturbation theory was employed in the main part of the work, and an upper limit for the contribution of all functions to the first and second order perturbation energies was obtained. This upper limit is 10 percent smaller than the experimental binding energy. It was then shown on the basis of variational calculations that perturbation theory, carried to this stage, over-shoots the mark, and the upper limit to the binding energy is reduced to 26 Mev, which is 6 Mev short of the experimental value. These figures are based on a set of nuclear constants which favor large mass defects. The perturbational effect of all doubly excited configurations upon the ${}_{}{}^3{}_{}{}^{}D$ state of ${\mathrm{Li}}^6$ was investigated and compared with the effect of similar functions upon the ${}_{}{}^3{}_{}{}^{}S$ state. The result is that the first order ${}_{}{}^3{}_{}{}^{}D-{}_{}{}^3{}_{}{}^{}S$ splitting, which is about 2 Mev, is enlarged to 6 Mev, both levels being depressed.