Preconcentration of low levels of americium and plutonium from waste waters by synthetic water-soluble metal-binding polymers with ultrafiltration

A preconcentration approach to assist in the measurement of low levels of americium and plutonium in waste waters has been developed based on the concept of using water-soluble metal-binding polymers in combination with ultrafiltration. The method has been optimized to give over 90% recovery and accountability from actual waste water.     

Optical lattice induced light shifts in an yb atomic clock

We present an experimental study of the lattice-induced light shifts on the (1)S(0) --> (3)P(0) optical clock transition (nu(clock) approximately 518 THz) in neutral ytterbium. The "magic" frequency nu(magic) for the 174Yb isotope was determined to be 394 799 475(35) MHz, which leads to a first order light shift uncertainty of 0.38 Hz. We also investigated the hyperpolarizability shifts due to the nearby 6s6p(3)P(0) --> 6s8p(3)P(0), 6s8p(3)P(2), and 6s5f(3)F(2) two-photon resonances at 759.708, 754.23, and 764.95 nm, respectively. By measuring the corresponding clock transition shifts near these two-photon resonances, the hyperpolarizability shift was estimated to be 170(33) mHz for a linear polarized, 50 microK deep, lattice at the magic wavelength. These results indicate that the differential polarizability and hyperpolarizability frequency shift uncertainties in a Yb lattice clock could be held to well below 10(-17).     

Recent atomic clock comparisons at NIST

The record of atomic clock frequency comparisons at NIST over the past half-decade provides one of the tightest constraints of any present-day temporal variations of the fundamental constants. Notably, the 6-year record of increasingly precise measurements of the absolute frequency of the Hg⁺ single-ion optical clock (using the cesium primary frequency standard NIST-F1) constrains the temporal variation of the fine structure constant α to less than 2 · 10⁻⁶yr⁻¹ and offers a Local Position Invariance test in the framework of General Relativity. The most recent measurement of the frequency ratio of the Al⁺ and Hg⁺ optical clocks is reported with a fractional frequency uncertainty of ±5.2 · 10⁻¹⁷. The record of such measurements over the last year sensitively tests for a temporal variation of α and constrains , consistent with zero.     

Thermal neutron activation: Sample preparation utilizing graphite as a diluent

A sample preparation method has been developed which produces both standard and unknown samples of the same size, shape, composition and density (a necessary condition for minimum error). A solution of standard or unknown material was pipetted onto graphite wetted with acetone, the material was dried and mixed with additional graphite to give a homogeneous mixture containing≥99% graphite. Portions of the mixture were pressed into uniform cylindrical pellets. Application of the method to the activation analysis of several copper compounds gave results which generally agreed with analysis by thiosulfate titration of liberated iodine to within less than 1%. This work was supported by the United States Atomic Energy Commission.     

Fast neutron activation: Sample preparation utilizing graphite as a diluent

A method has been developed for the preparation of irradiation samples which ensures that both standard and unknown samples are of the same size, shape, density and composition. Powdered standard and unknown samples were diluted with graphite to give homogeneous mixtures containing ≥80% graphite; these mixtures were pressed into cylindrical pellets. This method of sample preparation has been applied to the determination of nitrogen in organic and polymeric compounds. The results generally agree with Kjeldahl analyses within 5%. This work was supported by the United States Atomic Energy Commission.