Thermal neutron capture $\gamma$-ray spectra for ${}^{16,17,18}\mathrm{O}$ and ${}^2\mathrm{H}$ have been measured with guided cold neutron beams from the Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II) reactor and the Budapest Research Reactor (BRR) on natural and ${}^{17,18}\mathrm{O}$ enriched ${\mathrm{D}}_2\mathrm{O}$ targets. Complete neutron capture $\gamma$-ray decay schemes for the ${}^{16,17,18}\mathrm{O}$($\mathrm{n},\gamma$) reactions were measured. Absolute transition probabilities were determined for each reaction by a least-squares fit of the $\gamma$-ray intensities to the decay schemes after accounting for the contribution from internal conversion. The transition probability for the 870.76-keV $\gamma$ ray from ${}^{16}\mathrm{O}$($\mathrm{n},\gamma$) was measured as $P_{\gamma }\left(871\right)=96.6 \pm 0.5\%$ and the thermal neutron cross section for this $\gamma$ ray was determined as $0.164\pm 0.003$ mb by internal standardization with multiple targets containing oxygen and stoichiometric quantities of hydrogen, nitrogen, and carbon whose $\gamma$-ray cross sections were previously standardized. The $\gamma$-ray cross sections for the ${}^{17,18}\mathrm{O}$($\mathrm{n},\gamma$) and ${}^2\mathrm{H}$($\mathrm{n},\gamma$) reactions were then determined relative to the 870.76-keV $\gamma$-ray cross section after accounting for the isotopic abundances in the targets. We determined the following total radiative thermal neutron cross sections for each isotope from the $\gamma$-ray cross sections and transition probabilities; ${\sigma }_0({}^{16}\mathrm{O})=0.170\pm 0.003$ mb; ${\sigma }_0({}^{17}\mathrm{O})=0.67\pm 0.07$ mb; ${\sigma }_0({}^{18}\mathrm{O})=0.141\pm 0.006$ mb; and ${\sigma }_0({}^2\mathrm{H})=0.489\pm 0.006$ mb.

• Received 8 October 2015
• Revised 18 February 2016

DOI:https://doi.org/10.1103/PhysRevC.93.044311