Excitation Functions for Nuclear Reactions between Complex Nuclei. I. Neutron Emission

The excitation functions have been determined for the formation of ${\mathrm{Ce}}^{134}$, ${\mathrm{Ce}}^{135}$, and ${\mathrm{Ce}}^{137m}$ by the reactions ${\mathrm{Te}}^{128}$+${\mathrm{C}}^{12}$, ${\mathrm{Te}}^{130}$+${\mathrm{C}}^{12}$, and ${\mathrm{Sn}}^{124}$+${\mathrm{O}}^{16}$. The maximum cross sections were less than 0.6 b for all the reactions studied. The excitation functions appear to be displaced by 10 to 15 MeV higher in energy than expected for compound nucleus formation reactions of low angular momentum. This energy shift agrees with the "extra" energy measured by two other different techniques for the same Te+C system. This agreement provides good evidence that the effect of high angular momentum is to decrease de-excitation by neutron emission relative to that by gamma emission.