"Statistical Yrast Line" in Heavy-Ion Fusion Reactions

Fusion cross sections measured at high energies are parametrized in terms of a "statistical yrast line." This line lies parallel to the usual yrast line (given by the rigid-body moment of inertia, $\frac{2}{5}M{{\mathcal{r}}_0}^2{A}^{\frac{5}{3}}$) but is shifted upward by an additional energy $\Delta Q$. Most experimental fusion cross sections for systems with $A\lesssim 80$ are well reproduced with values of ${\mathcal{r}}_0=1.20\mathrm{}\pm 0.05$ fm and $\Delta Q=10\mathrm{}\pm 2.5$ MeV.