Accurate determination of traces of sodium and potassium in rocks by ion exchange followed by atomic absorption spectroscopy

Sodium and potassium (5–1000 p.p.m.) in rocks such as peridotites and dunites can be determined accurately by ion-exchange separation followed by atomic absorption spectrophotometry. The samples are decomposed in sulphuric, hydrochloric and hydrofluoric acid mixtures, and after removal of hydrofluoric acid the cations are absorbed on a 90-ml column of AG50W-X8 cation-exchange resin. Vanadium and other anion-forming elements are eluted with 0.01 M nitric acid containing hydrogen peroxide. Then the alkali metals are eluted with 0.50 M nitric acid, while Mg, Mn, Ca, Ti, Al, Fe and other multivalent elements are retained by the column. The eluate fractions containing the respective alkali metals are measured directly by atomic absorption spectrophotometry against standards in 0.50 M nitric acid. Relevant elution curves, results for synthetic mixtures and for three international rock standards are presented and discussed.     

Ion induced secondary electron emission from single crystal surfaces

Yields of ion impact induced electrons from very pure Ni(110) and Ni(111) surfaces have been measured. In several tilt planes the angle of incidence of a 5 keV H⁺, H⁺₂ or H⁺₃ ion beam is varied from perpendicular to grazing incidence. Below = 75° the yield increases as sec but shows characteristic depressions when the beam is incident along crystallographically low indexed lattice directions. This is explained by kinetic electron emission with respect to the projectile transparency of the crystal lattice.     

Electron density decay measurements using the 447.1 nm line of neutral helium

The 447.1 nm line of neutral helium has been used to measure the time-dependent decay of the electron density in the afterglow of a pulsed, atmospheric pressure helium discharge. The technique involves using a shutter which consists of a Pockels cell combined with crossed polarizers to gate the light pulse, allowing observation of the spectrum during various time windows in the discharge.     

Familien negativer vektorraumbündel und 1-konvexe abbildungen

Abhandlungen aus dem Mathematischen Seminar der Universität Hamburg -     

Procedures for a fast separation of berkelium from complex mixtures of reaction products

Two procedures are described for fast separations of berkelium from complex mixtures of reaction products arising from heavy ion reactions, such as¹⁸O+²⁴⁸Cm. The first procedure uses a combination of several extraction steps with a final separation on a cation exchanger, the second procedure starts with an anion exchange column which is followed by multiple extractions in different media. The elements separated in the different steps were analyzed and overall decontamination factors are given.     

Saturation of the dielectric absorption of vitreous silica at low temperatures

The dielectric absorption of vitreous silica containing 1200 ppm of OH^?-impurities has been measured at 10 GHz in the temperature range between 0.4 K and 8 K. A strong intensity dependence of the absorption coefficient has been observed at temperatures below 3 K.