Optical model analysis forO16+Pb208: Evidence for dynamic shape or density changes

For the reaction ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$, experimental data are available for cross sections for complete fusion and all reactions from 80-102 MeV and for elastic scattering from 80 to 313 MeV. Most of these data can be adequately described by an energy-independent spherical optical potential with the proximity formulation for the real part and a Woods-Saxon form for the imaginary part. Three parameters have been varied, radius and surface width in the proximity potential and radius in the imaginary potential. The sum of the equivalent sharp radii of the interacting nuclei must be enlarged significantly in order to fit the fusion and scattering data. As a consequence, the sum of the "best fit central radii" for ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ is ≈ 0.8 fm larger than the sum of the independently measured radii. If the proximity formulation is correct this implies dynamical shape or density adjustments during the collision.