Double-differential neutron emission cross sections of 14-MeV neutron induced reactions on Na and Pb

The energy and angular distribution of secondary neutrons from the interaction of 14-MeV neutrons with sodium and natural lead were investigated. Absolute double-differential neutron emission cross sections were measured for reaction angles from 30{degree} to 150{degree} in steps of 15{degree} in the secondary neutron energy range 2{endash}14 MeV using the time-of-flight facility at the Institut f{umlt u}r Radiumforschung und Kernphysik, Vienna. Systematic uncertainties in these measurements could be reduced to less than 3{endash}5{percent} (depending on secondary neutron energy) resulting in total uncertainties of less than 5{percent} for a large part of the studied range in angle and energy for Pb and of less than 8{percent} for Na. These results agree with previous measurements within the relatively large uncertainties of the latter. The measured cross sections were compared to the results of statistical model calculations using the quantum mechanical theory of Feshbach, Kerman, and Koonin for preequilibrium emission and also with calculations based on the exciton model and the Kalbach-Mann systematics for the shape of the angular distributions. For compound nucleus decay, the Hauser-Feshbach model was used in both cases. Very good agreement was found with both predictions in the case of lead; in the case of sodium, noticeable discrepancies do more » show the limits of applicability of any statistical model for light nuclei. {copyright} {ital 1997} {ital The American Physical Society} « less