Angular Distributions of (n,d) Pickup Reactions inN14,

Abstract

A double proportional counter-scintillator telescope was employed to study the angular distributions of deuterons produced by 14.1-MeV neutron-induced pickup reactions on natural targets of N 14 , P 31 , and S 32 . Measurements were taken at intervals of 5°-15° over the laboratory range 0°-150°. Simultaneous measurements of E and dE/dx permitted separation of particles of different Z/M. Five angular distributions of deuterons corresponding to three ground-state and two excited-state transitions were obtained. Absolute center-of-mass differential cross sections were assigned. Neither significant isotropic contributions nor back-angle yields were observed. All spin and parity assignments were consistent with accepted values. Absolute reduced widths were extracted by the peak-fitting method and the Amado extrapolation procedure. Comparison of experimental and jj shell-model S values (relative reduced widths), in addition to observed j[/-forbidden transitions, clearly indicated appreciable core excitations in the ground-state configurations of P 31 and S 32 . The S 32 (»,<f)P 31 (gnd.) measurements revealed a gross discrepancy in a previously reported cross section for the inverse P 31 (^,«)S 32 reaction. An anomalously large reduced width for the transition to the 3.68-MeV level of C 13 was qualitatively confirmed.