Systematics of nonequilibrium neutron emission

Neutron spectra have been obtained at various angles in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$, and ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ reactions leading to the ${}_{}{}^{170}{}_{}{}^{}\mathrm{Yb}$ compound nucleus between 4 and 11 MeV/nucleon above the Coulomb barrier. The energy and angular distributions can be fitted by a moving hot source model. However, this model does not consistently explain other systematic trends obtained by the analysis. The Boltzmann master equation model also does not provide an adequate fit to the data.