Thermal neutron capture cross sections for 16,17,18O and 2H

Thermal neutron capture gamma-ray spectra for O-16,O-17,O-18 and H-2 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 O-17,O-18 enriched D2O targets. Complete neutron capture gamma-ray decay schemes for the O-16,O-17,O-18(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 O-16(n, gamma) was measured as P-gamma(871) = 96.6 +/- 0.5% and the thermal neutron cross section for this gamma ray was determined as 0.164 +/- 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 O-17,O-18(n,gamma) and H-2(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)(O-16) = 0.170 +/- 0.003 mb; sigma(0)(O-17) = 0.67 +/- 0.07 mb; sigma(0)(O-18) = 0.141 +/- 0.006 mb; and sigma(0)(H-2) = 0.489 +/- 0.006 mb.