Pseudo Stark and uniaxial stress splitting of the 6955 Å zero-phonon line in LiF

The spectral resolution of quartz crystals bent to a cylindrical form by means of four rods was investigated with CuKα radiation in a reflection type arrangement. The crystal adjustment was made optically using interference fringes. With the crystal bent to a circular cylinder the deviations from exact focusing inherent to the Johann case could be measured and were found to be in agreement with theory. — Crystals bent to a logarithmic spiral have also been studied. With a 24 mm broad reflecting area (mean radius of curvature 1 m; (13¯40)-plane) an uncorrected full width at half maximum intensity of 0.43 XU or 2.25 eV was observed for the CuKα ₁ line, in agreement with double crystal spectrometer measurements.     

Separation and first structure elucidation of Cremophor EL-components by hyphenated capillary electrophoresis and delayed extraction-matrix assisted laser desorption/ionization-time of flight-mass spectrometry

The polyethoxylated heterogeneous components of the so far poorly characterized nonionic emulsifier Cremophor EL (polyoxyl 35 castor oil) (CrEL) were fractionated by cyclodextrin-modified micellar electrokinetic capillary chromatography (CD-MEKC). Due to the low UV absorbance of most of the CrEL-components an indirect UV detection was used with phenobarbital-sodium as background absorber. For a precise assignment of the resulting peaks to the corresponding components capillary electrophoresis (CE) had to be combined with delayed extraction-matrix assisted laser desorption/ionization-time of flight-mass spectrometry (DE-MALDI-TOF-MS) as detection system. For this purpose, the fractionating robot Probot was employed which enables both the on-line fractionation of the CE eluate on a MALDI target during the electrophoretic separation and the simultaneous dosage of the MALDI matrix solution. The applied CrEL amount was optimized by varying the CE injection parameters time, pressure and concentration of the sample in order to obtain homologue peak series of sufficient intensity without decreasing the separation efficiency. Evaluation of the mass spectra was performed by comparing the residue masses of the homologue peak series with the calculated residue masses of potential CrEL-components. However, the high number of polyethoxylated components leads to overlapping of homologue peak series with isobaric residue masses. These isobaric interferences were detected by a high mass accuracy of the measurements (obtained by internal calibration with polyethylene glycol (PEG) 1000 and by means of the residue mass plot, the newly developed evaluation method. The combination of these techniques allowed the first detailed structure analysis of the CrEL-components showing glycerol polyoxyethylene (POE) monoricinoleate and POE monoricinoleate to be the two main components of the emulsifier. Furthermore, the coupling of CE with DE-MALDI-TOF-MS is generally applicable to the fractionation and identification of polymers.     

N-Acylureido functionality as acceptor substituent in solvatochromic fluorescence probes: detection of carboxylic acids, alcohols, and fluoride ions

N,N'-Dicyclohexyl-N-(6'-methoxyanthryl-2-carbonyl)urea (1a) exhibits a strong solvatochromism with respect to its fluorescence properties. The emission maxima of 1a correlate well with the anion-stabilizing properties of the solvent. This feature allows the detection of analytes with high acceptor numbers, such as alcohols and carboxylic acids, and the detection of analytes such as fluoride ions which form strong hydrogen bonds with the amido hydrogen atom.     

Sequential associative information storage and reconstruction in a holographic circuit

After a brief discussion of the analogy between neutral and holographic information processing, a holographic circuit for associative information storage and reconstruction is described. This special system models the ability of the brain to reconstruct a sequence of previously stored informations A, B, C,…, when only one input stimulus is presented to the neural system. Furthermore the holographic system is capable of retrieving branching information, modelling the property of the brain to memorize various sequences of information with one special input.     

Ultrarot-Absorption und phononenfreie Übergänge in strahlungsverfärbtem LiF

Spectral positions, properties and behaviour of the lines and bands found in the infrared absorption of X-rayed LiF single crystals at 90°K are investigated. Thermal annealing and optical bleaching of the crystals give informations about the correlation of the lines and the bands. Both prove to be transitions in the same absorption centre. This agrees well with the fact that the lines are due to phonon-free transitions in colour centres, whilst the bands are broadened by multiphonon processes. For the thermal annealing process of the infrared absorption a characteristic temperature of 420°K and an activation energy of 0·44 eV for the recombination process can be calculated by analysing isochrone annealing curves. According to their similar behaviour the infrared bands are compared with theR-centre absorption.     

A trigonal color center in NaF

Uniaxial stress splitting experiments suggest the 5456 Å zero-phonon line in NaF to be due to a transition of the F ₃ ⁺ center. The line and a number of phonon-assisted peaks are observed in absorption and emission.