Neutron capture measurements were made for bismuth samples up to the inelastic scattering threshold at 901 keV (lab). All resonance peaks ($l=0,1$) between 2.6 and 30 keV were fitted to single level parameters by least squares adjustment. From 30 to 70 keV the resonances reported from recent neutron transmission studies were fitted. Average radiative widths found were (164 ± 45) meV for $l=0$ and (33.7 ± 3) meV for $l\ge 1$. The average spacing of $l>\mathrm{}0\mathrm{}$ levels was 1.14 ± 0.25 keV for the energy interval 2.6-30 keV. The astrophysical average capture (10.7 mb at $\mathrm{kT}=30$ keV) is little different from earlier estimates but the rate of change with stellar temperature is slower.

NUCLEAR REACTIONS ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}(n,\gamma )$, $E=2.6-901\mathrm{}$ keV; measured $\sigma \mathrm{}\left(E\right)\mathrm{}$; deduced ${}_{}{}^{210}{}_{}{}^{}\mathrm{Bi}$ level parameters, average radiative widths, $p$-wave spacing.

• Received 24 May 1976

DOI:https://doi.org/10.1103/PhysRevC.14.1389