A method to extract simultaneously level densities and $\gamma$-ray transmission coefficients has for the first time been tested on light nuclei utilizing the $^{ 28}$Si($^3$He,$\alpha\gamma)^{ 27}$Si and $^{ 28}$Si($^3$He,$^3$He'$\gamma)^{ 28}$Si reactions. The extracted level densities for $^{ 27}$Si and $^{ 28}$Si are consistent with the level densities obtained by counting known levels in the respective nuclei. The extracted $\gamma$-ray strength in $^{ 28}$Si agrees well with the known $\gamma$-decay properties of this nucleus. Typical nuclear temperatures are found to be $T\sim 2.4$ MeV at around 7 MeV excitation energy. The entropy gap between nuclei with mass number $A$ and $A\pm 1$ is measured to be $\delta S\sim 1.0 k_B$, which indicates an energy spacing between single-particle orbitals comparable with typical nuclear temperatures.
Categories: nucl-ex