15N(n,d)14C and 15N(n,t)13C ground state reactions as functions of energy and angle in the neutron energy range 13.6 to 14.8 MeV

This study was undertaken in order to determine the mechanism of the 15N(n,d)14C g.s. reaction and to investigate the 15N(n,t)13C g.s. reaction. Techniques were developed for producing neutron spectra having the characteristics needed for excitation function measurements. A method was also developed for measuring the neutron spectrum incident on a reaction target. The 15N reaction data were taken with a counter telescope which consisted of two gas differential energy detectors plus a scintillator. Excitation functions were measured at counter angle settings of 00 and 450 over the neutron energy range 13.6 through 14.8 meV. Cross section angular distributions were taken at anti E/sub n/ = 14.1 and 14.6 MeV. The direct mechanism was found to be completely dominant for the (n,d) reaction. A DWBA analysis gives a fairly good fit to the shape of the observed angular distribution for 15N(n,d)14C g.s., but predicts an energy dependence different from that observed. Spectroscopic factors extracted for the (n,d) reaction are ambiguous because of sensitivity to the choice of 14C + d optical potential. The absolute cross section observed for 15N(n,d)14C g.s. is contradictory to the results of earlier work on 14C(d,n)15N g.s. A significant variation seen in the 00 excitation function for 15N(n,t)13C g.s. was deduced to be a compound nucleus-related statistical fluctuation. Values for fractional direct mechanism contributions to the energy-averaged (n,t) cross sections were extracted, as were values for the mean level width of the 16N compound nucleus. Cross sections for 15N(n,t)13C g.s. were calculated in zero-range DWBA. The factors required to normalize the theoretical cross sections are in all cases several times larger than standard values