Cross sections at six angles between 0° and 19° in the center-of-mass system have been measured for the ground-state transition in the reaction ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$(n,p${)}^{13}$B at ${\mathit{E}}_{\mathit{n}}$=118 MeV. The 0° cross section gives a value of 186±25 MeV ${\mathrm{fm}}^3$ for the volume integral of the spin-isospin component of the central part of the effective N-N interaction. The theoretical value is 161 MeV ${\mathrm{fm}}^3$ at 100 MeV. A distorted-wave impulse-approximation calculation for the angular distribution of the ground-state transition, (1/$2^{\mathrm{-}}$,1/2) to (3/$2^{\mathrm{-}}$,3/2), compares well with the measurement. The 0° measurement is compared with other (n,p) and (p,n) measurements on ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ to test the universal proportionality of these cross sections to the inverse β decay. A falloff in the proportionality constant in going to low energy is confirmed. © 1996 The American Physical Society.

• Received 19 October 1995

DOI:https://doi.org/10.1103/PhysRevC.54.2767