On the retrograde condensation of one or two liquids

This contribution discusses the phenomena of retrograde condensation of one or two liquids. It w1 be shown that both phenomena can be well understood. Also the relation of retrograde condensation of one liquid phase with the condensation behavior of natural gas will be discussed. Similarly that of two liquid phases with multiple phase behavior occurring in low temperature reservoir fluids will be pointed out.     

Infrared absorption spectrum of a small-polaron system

Characteristic features and the temperature dependence of the small-polaron absorption spectrum are discussed using a recently published model. The physical interpretation of formal results is introduced, in particular a connection of small-polaron states with oscillator coherent states is emphasized. The continuous change of absorption curves with temperature is illustrated by numerical calculations.     

Does ionized diacetylene have a positive proton affinity?

Singly and doubly charged C₄H₃^+/2+ ions generated upon electron ionization (EI) of the neutral precursors 1,3-butadiene, benzene, and exo-methylene cyclopropane, respectively, are examined by sector-field mass-spectrometry. Charge stripping of the mass-selected monocations affords the corresponding dications and charge exchange of the C₄H₃²⁺ dications allows for the reverse redox process. Refined analysis and additional MS/MS studies suggest that the monocations are mixtures of isomeric ions formed upon ionization, whereas only a single type of dication seems to be formed. As an average of energy-resolved measurements, a vertical ionization energy of IE_v(C₄H₃⁺)=16.5±0.4 eV is derived. In addition to the experimental work, density functional theory is used for a computational exploration of the mono- and dicationic species. The best theoretical estimates are IE_a(C₄H₃⁺)=16.33 eV and IE_v(C₄H₃⁺)=16.49 eV for the most stable isomer H₂C=C---CCH⁺. Combination of the experimental and theoretical findings leads to the conclusion that the diacetylene cation C₄H₂⁺ has indeed a positive proton affinity of PA(C₄H₂⁺)=1.50±0.42 eV.     

40Ar/39Ar — Alter eines Basits der Ostantarktis

The⁴⁰Ar/³⁹Ar technique is an analytical variation of the K–Ar dating method. A known fraction of the³⁹K in a sample is converted to³⁹Ar by irradiation with fast neutrons. In an incremental heating experiment, the argon is released from the sample fractionally by stepwise heating. The result is a series of apparent ages.⁴⁰Ar/³⁹Ar age spectrum was determined for the sample Oase Vestfold. The minimum of the saddle-shaped age spectrum gives 1.0 billion years.     

Ambident reactivity of the thiocyanate anion revisited: can the product ratio be explained by the hard soft acid base principle?

Laser flash photolysis and stopped-flow methods have been employed to determine the kinetics of the reactions of benzhydrylium ions with both termini of the thiocyanate ion. In contrast to previous investigations which reported sulfur/nitrogen ratios of k(S)/k(N) = 2-10 for the reactions of carbocations with SCN(-), values of k(S)/k(N) = 10(3)-10(4) are now derived from absolute rate constants. This discrepancy is explained by the fact that the data determined in this investigation are the first which refer to activation-controlled attack of carbocations at both termini of the thiocyanate ion, while previous reactivity ratios included diffusion-controlled reactions. It is concluded that the selectivities of the reactions of carbocations with the thiocyanate ion cannot be explained by the hard soft acid base principle.     

Construction of functional porphyrin polystyrene nano-architectures by ATRP

A series of mono-functionalized metallo-porphyrin polystyrenes have been synthesized using atom transfer radical polymerization and their self-assembling behavior was studied by electron microscopy showing that the polystyrene tail-length influences the aggregate architecture.     

Ein Automatisiertes Mess-System für die Ge(Li)-Gammaspektrometrie

An automated off-line Ge(Li)-spectrometer is described. Its special features are a sample changer with rotating disk store and pneumatic tube, a self-controlling source—detector distance and an autonomous control programmed by cable connections or by punched tape via a central control unit. The system is meant to do complex routine work in activity supervision and activation analysis.