Angular Distributions of (n,d) Pickup Reactions in N14, P31, and S32 at 14 MeV

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 ${\mathrm{N}}^{14}$, ${\mathrm{P}}^{31}$, and ${\mathrm{S}}^{32}$. Measurements were taken at intervals of 5°-15° over the laboratory range 0°-150°. Simultaneous measurements of $E$ and $\frac{\mathrm{dE}}{\mathrm{dx}}$ permitted separation of particles of different $\frac{Z}{M}$. 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 $\mathrm{jj}$ shell-model $S$ values (relative reduced widths), in addition to observed $\mathrm{jj}$-forbidden transitions, clearly indicated appreciable core excitations in the ground-state configurations of ${\mathrm{P}}^{31}$ and ${\mathrm{S}}^{32}$. The ${\mathrm{S}}^{32}\mathrm{}(n,d)\mathrm{}{\mathrm{P}}^{31}$ (gnd.) measurements revealed a gross discrepancy in a previously reported cross section for the inverse ${\mathrm{P}}^{31}\mathrm{}(d,n)\mathrm{}{\mathrm{S}}^{32}$ reaction. An anomalously large reduced width for the transition to the 3.68-MeV level of ${\mathrm{C}}^{13}$ was qualitatively confirmed.