RESUMO
A new reference material was characterized for 229Th molality and thorium isotope amount ratios. This reference material is intended for use in nuclear forensic analyses as an isotope dilution mass spectrometry spike. The reference material value and expanded uncertainty (k = 2) for the 229Th molality is (1.1498 ± 0.0016) × 10-10molg-1 solution. The value and expanded uncertainty (k = 2) for the n(230Th)/n(229Th) ratio is (5.18 ± 0.26) × 10-5 and the n(232Th)/n(229Th) ratio is (3.815 ± 0.092) × 10-4.
RESUMO
A new determination of the 229Th half-life was made based on measurements of the 229Th massic activity of a high-purity solution for which the 229Th molality had previously been measured. The 229Th massic activity was measured by direct comparison with SRM 4328C using 4παß liquid scintillation counting, NaI counting, and standard addition liquid scintillation counting. The massic activity was confirmed by isotope dilution alpha spectrometry measurements. The calculated 229Th half-life is (7825 ± 87) years (k = 2), which is shorter than the three most recent half-life determinations but is consistent with these values within uncertainties.
RESUMO
A proton NMR titration study is presented where in small increments quantities of water were added to "dry" CmEn nonionic surfactant. For a particular range of compositions, two resonances for the water/hydroxyl protons were observed that display large chemical shift increases as water content is increased indicating that water must partition between two chemical environments with a surprisingly slow chemical exchange rate. A detailed mechanism of how the increasing amounts of water are incorporated into the surfactant medium is presented accounting for all observed spectral changes.