Nucleon-Core Polarization in the Calculation of the Strength Function

The model of Lane, Thomas, and Wigner, for the excited states of nuclei, is generalized by the introduction of a variable amount of nucleon-core polarization into the states of the independent-particle model. The mixing of each of the polarized states, by configuration interaction, into a small neighborhood near the initial energy of the state forms the basis of our model. The energy moments of the strength function are calculated. The second moment of the strength function, which may be roughly equal to the square of the full width at half-maximum of the strength function, is calculated approximately using a two-body Yukawa potential without exchange. By the choice of a suitable amount of core polarization the large value obtained by Lane, Thomas, and Wigner for the second moment [(${22\mathrm{M}\mathrm{e}\mathrm{v})}^2$] is reduced by a factor of 23 to the reasonably small value of (${4.8\mathrm{M}\mathrm{e}\mathrm{v})}^2$.