Titanium and carbon implantation of iron

Pure iron foils have been implanted with Ti and with Ti plus C and characterized by conversion electron Mössbauer spectroscopy (CEMS) and Auger electron spectroscopy (AES). Both paramagnetic and magnetic phases are observed and attributed to amorphous Fe?Ti?C alloys of differing Ti and C contents. Estimates of the thicknesses of the amorphous layers based on the CEMS data are in good agreement with the AES concentration depth profiles.     

VUV laser-induced fluorescence of molecular hydrogen

State-selective detection of molecular hydrogen by VUV laser-induced fluorescence has been achieved at excitation wavelengths greater than the lithium fluoride cut-off, using xenon as the non-linear medium. With this approach sensitivities of ≈10⁹ per cm³ per quantum state have been achieved under cell conditions. This method provides a simple approach to monitoring the vibrational state distribution of hydrogen and its isotopes.     

Chemoselective reductive alkylation of ammonia with carbonyl compounds: synthesis of primary and symmetrical secondary amines

An efficient, general procedure for highly chemoselective reductive mono-alkylation of ammonia with ketones is reported. Treatment of ketones with ammonia in ethanol and titanium(IV) isopropoxide, followed by in situ sodium borohydride reduction, and a straightforward workup afforded primary amines in good to excellent yields. Reductive alkylation of ammonia with aldehydes, on the other hand, afforded the corresponding symmetrical secondary amines selectively.     

Comparison of laser microprobe mass spectrometry and fast-atom-bombardment mass spectrometry for organic analysis

Both the techniques mentioned provide molecular weight and structural information, but laser microprobe mass spectrometry (LMMS) also provides greater control over the degree of fragmentation and enhanced sensitivity. In addition, LMMS allows microprobe analysis (i.e., spatial resolution of a few μm²) as well as providing quantitative measurements. The less energetic nature of fast-atom-bombardment mass spectrometry (FAB-MS) makes it more suitable for the analysis of highly labile polar compounds and high-mass biopolymers.     

Generation of alternating groups by pairs of conjugates

Considering the conjugacy classes of the alternating group of degreen, those classes that contain a pair of generators are in the majority. In fact, the proportion of such classes is 1 –(n), and(n) 0 asn .     

The double-bond in ethylene

A full configuration interaction treatment has been carried out for the four electrons of the double bond of ethylene using a minimal STO basis set. The excent to which - separability provides a good approximation for the eigenfunctions of the low-lying states and for transitions between them has been examined. Alternative formulations using various more localised orbitals as the basis are derived for a number of the states. These have been examined and discussed.

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Zusammenfassung Eine vollständige Konfigurationswechselwirkung wurde für die vier Elektronen der Doppelbindung von Äthylen durchgeführt, wobei eine minimale STO-Basis benutzt wurde. Das Maß, in dem die --Separierbarkeit eine gute Näherung für Eigenfunktionen der niedrigliegenden Zustände und für Übergänge zwischen ihnen darstellt, wurde untersucht. Alternativformulierungen, die verschiedene, lokalisierte Orbitale als Basis benutzen, werden für eine Anzahl von Zuständen angegeben und diskutiert.

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Résumé Interaction de configuration complète pour les quatre électrons de la double liaison de l'éthylène dans une base STO minimale. La séparabilité - est examinée pour les plus bas états et les transitions entre ces états. D'autres formulations utilisant des orbitales plus localisées sont obtenues pour certains états. Ces formulations sont discutées.

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We wish to thank the Instituto de Alta Cultura of Portugal for a scholarship for A. A. and the National Science Foundation (USA) for a post-doctoral fellowship for C.T.W.